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Publisher: John Wiley and Sons   (Total: 1597 journals)

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Showing 1 - 200 of 1597 Journals sorted alphabetically
Abacus     Hybrid Journal   (Followers: 13, SJR: 0.48, h-index: 22)
About Campus     Hybrid Journal   (Followers: 5)
Academic Emergency Medicine     Hybrid Journal   (Followers: 67, SJR: 1.385, h-index: 91)
Accounting & Finance     Hybrid Journal   (Followers: 49, SJR: 0.547, h-index: 30)
ACEP NOW     Free   (Followers: 1)
Acta Anaesthesiologica Scandinavica     Hybrid Journal   (Followers: 55, SJR: 1.02, h-index: 88)
Acta Archaeologica     Hybrid Journal   (Followers: 175, SJR: 0.101, h-index: 9)
Acta Geologica Sinica (English Edition)     Hybrid Journal   (Followers: 3, SJR: 0.552, h-index: 41)
Acta Neurologica Scandinavica     Hybrid Journal   (Followers: 5, SJR: 1.203, h-index: 74)
Acta Obstetricia et Gynecologica Scandinavica     Hybrid Journal   (Followers: 14, SJR: 1.197, h-index: 81)
Acta Ophthalmologica     Hybrid Journal   (Followers: 7, SJR: 0.112, h-index: 1)
Acta Paediatrica     Hybrid Journal   (Followers: 56, SJR: 0.794, h-index: 88)
Acta Physiologica     Hybrid Journal   (Followers: 6, SJR: 1.69, h-index: 88)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Acta Psychiatrica Scandinavica     Hybrid Journal   (Followers: 37, SJR: 2.518, h-index: 113)
Acta Zoologica     Hybrid Journal   (Followers: 7, SJR: 0.459, h-index: 29)
Acute Medicine & Surgery     Hybrid Journal   (Followers: 5)
Addiction     Hybrid Journal   (Followers: 36, SJR: 2.086, h-index: 143)
Addiction Biology     Hybrid Journal   (Followers: 15, SJR: 2.091, h-index: 57)
Adultspan J.     Hybrid Journal   (SJR: 0.127, h-index: 4)
Advanced Energy Materials     Hybrid Journal   (Followers: 26, SJR: 6.411, h-index: 86)
Advanced Engineering Materials     Hybrid Journal   (Followers: 28, SJR: 0.81, h-index: 81)
Advanced Functional Materials     Hybrid Journal   (Followers: 51, SJR: 5.21, h-index: 203)
Advanced Healthcare Materials     Hybrid Journal   (Followers: 14, SJR: 0.232, h-index: 7)
Advanced Materials     Hybrid Journal   (Followers: 283, SJR: 9.021, h-index: 345)
Advanced Materials Interfaces     Hybrid Journal   (Followers: 6, SJR: 1.177, h-index: 10)
Advanced Optical Materials     Hybrid Journal   (Followers: 7, SJR: 2.488, h-index: 21)
Advanced Science     Open Access   (Followers: 5)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 18, SJR: 2.729, h-index: 121)
Advances in Polymer Technology     Hybrid Journal   (Followers: 14, SJR: 0.344, h-index: 31)
Africa Confidential     Hybrid Journal   (Followers: 21)
Africa Research Bulletin: Economic, Financial and Technical Series     Hybrid Journal   (Followers: 13)
Africa Research Bulletin: Political, Social and Cultural Series     Hybrid Journal   (Followers: 11)
African Development Review     Hybrid Journal   (Followers: 33, SJR: 0.275, h-index: 17)
African J. of Ecology     Hybrid Journal   (Followers: 16, SJR: 0.477, h-index: 39)
Aggressive Behavior     Hybrid Journal   (Followers: 17, SJR: 1.391, h-index: 66)
Aging Cell     Open Access   (Followers: 11, SJR: 4.374, h-index: 95)
Agribusiness : an Intl. J.     Hybrid Journal   (Followers: 3, SJR: 0.627, h-index: 14)
Agricultural and Forest Entomology     Hybrid Journal   (Followers: 16, SJR: 0.925, h-index: 43)
Agricultural Economics     Hybrid Journal   (Followers: 45, SJR: 1.099, h-index: 51)
AIChE J.     Hybrid Journal   (Followers: 32, SJR: 1.122, h-index: 120)
Alcoholism and Drug Abuse Weekly     Hybrid Journal   (Followers: 7)
Alcoholism Clinical and Experimental Research     Hybrid Journal   (Followers: 7, SJR: 1.416, h-index: 125)
Alimentary Pharmacology & Therapeutics     Hybrid Journal   (Followers: 34, SJR: 2.833, h-index: 138)
Alimentary Pharmacology & Therapeutics Symposium Series     Hybrid Journal   (Followers: 3)
Allergy     Hybrid Journal   (Followers: 50, SJR: 3.048, h-index: 129)
Alternatives to the High Cost of Litigation     Hybrid Journal   (Followers: 3)
American Anthropologist     Hybrid Journal   (Followers: 153, SJR: 0.951, h-index: 61)
American Business Law J.     Hybrid Journal   (Followers: 24, SJR: 0.205, h-index: 17)
American Ethnologist     Hybrid Journal   (Followers: 93, SJR: 2.325, h-index: 51)
American J. of Economics and Sociology     Hybrid Journal   (Followers: 30, SJR: 0.211, h-index: 26)
American J. of Hematology     Hybrid Journal   (Followers: 35, SJR: 1.761, h-index: 77)
American J. of Human Biology     Hybrid Journal   (Followers: 13, SJR: 1.018, h-index: 58)
American J. of Industrial Medicine     Hybrid Journal   (Followers: 16, SJR: 0.993, h-index: 85)
American J. of Medical Genetics Part A     Hybrid Journal   (Followers: 17, SJR: 1.115, h-index: 61)
American J. of Medical Genetics Part B: Neuropsychiatric Genetics     Hybrid Journal   (Followers: 4, SJR: 1.771, h-index: 107)
American J. of Medical Genetics Part C: Seminars in Medical Genetics     Partially Free   (Followers: 6, SJR: 2.315, h-index: 79)
American J. of Physical Anthropology     Hybrid Journal   (Followers: 38, SJR: 1.41, h-index: 88)
American J. of Political Science     Hybrid Journal   (Followers: 302, SJR: 5.101, h-index: 114)
American J. of Primatology     Hybrid Journal   (Followers: 14, SJR: 1.197, h-index: 63)
American J. of Reproductive Immunology     Hybrid Journal   (Followers: 4, SJR: 1.347, h-index: 75)
American J. of Transplantation     Hybrid Journal   (Followers: 19, SJR: 2.792, h-index: 140)
American J. on Addictions     Hybrid Journal   (Followers: 10, SJR: 0.843, h-index: 57)
Anaesthesia     Hybrid Journal   (Followers: 146, SJR: 1.404, h-index: 88)
Analyses of Social Issues and Public Policy     Hybrid Journal   (Followers: 10, SJR: 0.397, h-index: 18)
Analytic Philosophy     Hybrid Journal   (Followers: 20)
Anatomia, Histologia, Embryologia: J. of Veterinary Medicine Series C     Hybrid Journal   (Followers: 3, SJR: 0.295, h-index: 27)
Anatomical Sciences Education     Hybrid Journal   (Followers: 1, SJR: 0.633, h-index: 24)
Andrologia     Hybrid Journal   (Followers: 2, SJR: 0.528, h-index: 45)
Andrology     Hybrid Journal   (Followers: 2, SJR: 0.979, h-index: 14)
Angewandte Chemie     Hybrid Journal   (Followers: 176)
Angewandte Chemie Intl. Edition     Hybrid Journal   (Followers: 239, SJR: 6.229, h-index: 397)
Animal Conservation     Hybrid Journal   (Followers: 41, SJR: 1.576, h-index: 62)
Animal Genetics     Hybrid Journal   (Followers: 8, SJR: 0.957, h-index: 67)
Animal Science J.     Hybrid Journal   (Followers: 6, SJR: 0.569, h-index: 24)
Annalen der Physik     Hybrid Journal   (Followers: 5, SJR: 1.46, h-index: 40)
Annals of Anthropological Practice     Partially Free   (Followers: 2, SJR: 0.187, h-index: 5)
Annals of Applied Biology     Hybrid Journal   (Followers: 7, SJR: 0.816, h-index: 56)
Annals of Clinical and Translational Neurology     Open Access   (Followers: 1)
Annals of Gastroenterological Surgery     Open Access  
Annals of Human Genetics     Hybrid Journal   (Followers: 9, SJR: 1.191, h-index: 67)
Annals of Neurology     Hybrid Journal   (Followers: 49, SJR: 5.584, h-index: 241)
Annals of Noninvasive Electrocardiology     Hybrid Journal   (Followers: 1, SJR: 0.531, h-index: 38)
Annals of Public and Cooperative Economics     Hybrid Journal   (Followers: 8, SJR: 0.336, h-index: 23)
Annals of the New York Academy of Sciences     Hybrid Journal   (Followers: 5, SJR: 2.389, h-index: 189)
Annual Bulletin of Historical Literature     Hybrid Journal   (Followers: 12)
Annual Review of Information Science and Technology     Hybrid Journal   (Followers: 14)
Anthropology & Education Quarterly     Hybrid Journal   (Followers: 26, SJR: 0.72, h-index: 31)
Anthropology & Humanism     Hybrid Journal   (Followers: 18, SJR: 0.137, h-index: 3)
Anthropology News     Hybrid Journal   (Followers: 15)
Anthropology of Consciousness     Hybrid Journal   (Followers: 11, SJR: 0.172, h-index: 5)
Anthropology of Work Review     Hybrid Journal   (Followers: 11, SJR: 0.256, h-index: 5)
Anthropology Today     Hybrid Journal   (Followers: 94, SJR: 0.545, h-index: 15)
Antipode     Hybrid Journal   (Followers: 54, SJR: 2.212, h-index: 69)
Anz J. of Surgery     Hybrid Journal   (Followers: 8, SJR: 0.432, h-index: 59)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apmis     Hybrid Journal   (Followers: 1, SJR: 0.855, h-index: 73)
Applied Cognitive Psychology     Hybrid Journal   (Followers: 74, SJR: 0.754, h-index: 69)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7, SJR: 0.632, h-index: 58)
Applied Psychology     Hybrid Journal   (Followers: 167, SJR: 1.023, h-index: 64)
Applied Psychology: Health and Well-Being     Hybrid Journal   (Followers: 53, SJR: 0.868, h-index: 13)
Applied Stochastic Models in Business and Industry     Hybrid Journal   (Followers: 5, SJR: 0.613, h-index: 24)
Aquaculture Nutrition     Hybrid Journal   (Followers: 12, SJR: 1.025, h-index: 55)
Aquaculture Research     Hybrid Journal   (Followers: 31, SJR: 0.807, h-index: 60)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 36, SJR: 1.047, h-index: 57)
Arabian Archaeology and Epigraphy     Hybrid Journal   (Followers: 12, SJR: 0.453, h-index: 11)
Archaeological Prospection     Hybrid Journal   (Followers: 12, SJR: 0.922, h-index: 21)
Archaeology in Oceania     Hybrid Journal   (Followers: 13, SJR: 0.745, h-index: 18)
Archaeometry     Hybrid Journal   (Followers: 31, SJR: 0.809, h-index: 48)
Archeological Papers of The American Anthropological Association     Hybrid Journal   (Followers: 15, SJR: 0.156, h-index: 2)
Architectural Design     Hybrid Journal   (Followers: 29, SJR: 0.261, h-index: 9)
Archiv der Pharmazie     Hybrid Journal   (Followers: 3, SJR: 0.628, h-index: 43)
Archives of Drug Information     Hybrid Journal   (Followers: 5)
Archives of Insect Biochemistry and Physiology     Hybrid Journal   (SJR: 0.768, h-index: 54)
Area     Hybrid Journal   (Followers: 13, SJR: 0.938, h-index: 57)
Art History     Hybrid Journal   (Followers: 273, SJR: 0.153, h-index: 13)
Arthritis & Rheumatology     Hybrid Journal   (Followers: 56, SJR: 1.984, h-index: 20)
Arthritis Care & Research     Hybrid Journal   (Followers: 29, SJR: 2.256, h-index: 114)
Artificial Organs     Hybrid Journal   (Followers: 1, SJR: 0.872, h-index: 60)
ASHE Higher Education Reports     Hybrid Journal   (Followers: 16)
Asia & the Pacific Policy Studies     Open Access   (Followers: 17)
Asia Pacific J. of Human Resources     Hybrid Journal   (Followers: 329, SJR: 0.494, h-index: 19)
Asia Pacific Viewpoint     Hybrid Journal   (Followers: 1, SJR: 0.616, h-index: 26)
Asia-Pacific J. of Chemical Engineering     Hybrid Journal   (Followers: 8, SJR: 0.345, h-index: 20)
Asia-pacific J. of Clinical Oncology     Hybrid Journal   (Followers: 6, SJR: 0.554, h-index: 14)
Asia-Pacific J. of Financial Studies     Hybrid Journal   (SJR: 0.241, h-index: 7)
Asia-Pacific Psychiatry     Hybrid Journal   (Followers: 4, SJR: 0.377, h-index: 7)
Asian Economic J.     Hybrid Journal   (Followers: 8, SJR: 0.234, h-index: 21)
Asian Economic Policy Review     Hybrid Journal   (Followers: 4, SJR: 0.196, h-index: 12)
Asian J. of Control     Hybrid Journal   (SJR: 0.862, h-index: 34)
Asian J. of Endoscopic Surgery     Hybrid Journal   (Followers: 1, SJR: 0.394, h-index: 7)
Asian J. of Organic Chemistry     Hybrid Journal   (Followers: 6, SJR: 1.443, h-index: 19)
Asian J. of Social Psychology     Hybrid Journal   (Followers: 6, SJR: 0.665, h-index: 37)
Asian Politics and Policy     Hybrid Journal   (Followers: 12, SJR: 0.207, h-index: 7)
Asian Social Work and Policy Review     Hybrid Journal   (Followers: 5, SJR: 0.318, h-index: 5)
Asian-pacific Economic Literature     Hybrid Journal   (Followers: 5, SJR: 0.168, h-index: 15)
Assessment Update     Hybrid Journal   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 3, SJR: 0.701, h-index: 40)
Atmospheric Science Letters     Open Access   (Followers: 30, SJR: 1.332, h-index: 27)
Austral Ecology     Hybrid Journal   (Followers: 15, SJR: 1.095, h-index: 66)
Austral Entomology     Hybrid Journal   (Followers: 9, SJR: 0.524, h-index: 28)
Australasian J. of Dermatology     Hybrid Journal   (Followers: 8, SJR: 0.714, h-index: 40)
Australasian J. On Ageing     Hybrid Journal   (Followers: 6, SJR: 0.39, h-index: 22)
Australian & New Zealand J. of Statistics     Hybrid Journal   (Followers: 14, SJR: 0.275, h-index: 28)
Australian Accounting Review     Hybrid Journal   (Followers: 3, SJR: 0.709, h-index: 14)
Australian and New Zealand J. of Family Therapy (ANZJFT)     Hybrid Journal   (Followers: 3, SJR: 0.382, h-index: 12)
Australian and New Zealand J. of Obstetrics and Gynaecology     Hybrid Journal   (Followers: 46, SJR: 0.814, h-index: 49)
Australian and New Zealand J. of Public Health     Hybrid Journal   (Followers: 13, SJR: 0.82, h-index: 62)
Australian Dental J.     Hybrid Journal   (Followers: 6, SJR: 0.482, h-index: 46)
Australian Economic History Review     Hybrid Journal   (Followers: 6, SJR: 0.171, h-index: 12)
Australian Economic Papers     Hybrid Journal   (Followers: 31, SJR: 0.23, h-index: 9)
Australian Economic Review     Hybrid Journal   (Followers: 6, SJR: 0.357, h-index: 21)
Australian Endodontic J.     Hybrid Journal   (Followers: 3, SJR: 0.513, h-index: 24)
Australian J. of Agricultural and Resource Economics     Hybrid Journal   (Followers: 3, SJR: 0.765, h-index: 36)
Australian J. of Grape and Wine Research     Hybrid Journal   (Followers: 5, SJR: 0.879, h-index: 56)
Australian J. of Politics & History     Hybrid Journal   (Followers: 15, SJR: 0.203, h-index: 14)
Australian J. of Psychology     Hybrid Journal   (Followers: 18, SJR: 0.384, h-index: 30)
Australian J. of Public Administration     Hybrid Journal   (Followers: 443, SJR: 0.418, h-index: 29)
Australian J. of Rural Health     Hybrid Journal   (Followers: 6, SJR: 0.43, h-index: 34)
Australian Occupational Therapy J.     Hybrid Journal   (Followers: 75, SJR: 0.59, h-index: 29)
Australian Psychologist     Hybrid Journal   (Followers: 11, SJR: 0.331, h-index: 31)
Australian Veterinary J.     Hybrid Journal   (Followers: 23, SJR: 0.459, h-index: 45)
Autism Research     Hybrid Journal   (Followers: 38, SJR: 2.126, h-index: 39)
Autonomic & Autacoid Pharmacology     Hybrid Journal   (SJR: 0.371, h-index: 29)
Banks in Insurance Report     Hybrid Journal   (Followers: 1)
Basic & Clinical Pharmacology & Toxicology     Hybrid Journal   (Followers: 11, SJR: 0.539, h-index: 70)
Basic and Applied Pathology     Open Access   (Followers: 2, SJR: 0.113, h-index: 4)
Basin Research     Hybrid Journal   (Followers: 5, SJR: 1.54, h-index: 60)
Bauphysik     Hybrid Journal   (Followers: 2, SJR: 0.194, h-index: 5)
Bauregelliste A, Bauregelliste B Und Liste C     Hybrid Journal  
Bautechnik     Hybrid Journal   (Followers: 1, SJR: 0.321, h-index: 11)
Behavioral Interventions     Hybrid Journal   (Followers: 10, SJR: 0.297, h-index: 23)
Behavioral Sciences & the Law     Hybrid Journal   (Followers: 23, SJR: 0.736, h-index: 57)
Berichte Zur Wissenschaftsgeschichte     Hybrid Journal   (Followers: 10, SJR: 0.11, h-index: 5)
Beton- und Stahlbetonbau     Hybrid Journal   (Followers: 2, SJR: 0.493, h-index: 14)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 6, SJR: 0.311, h-index: 26)
Bioelectromagnetics     Hybrid Journal   (Followers: 1, SJR: 0.568, h-index: 64)
Bioengineering & Translational Medicine     Open Access  
BioEssays     Hybrid Journal   (Followers: 10, SJR: 3.104, h-index: 155)
Bioethics     Hybrid Journal   (Followers: 14, SJR: 0.686, h-index: 39)
Biofuels, Bioproducts and Biorefining     Hybrid Journal   (Followers: 1, SJR: 1.725, h-index: 56)
Biological J. of the Linnean Society     Hybrid Journal   (Followers: 18, SJR: 1.172, h-index: 90)
Biological Reviews     Hybrid Journal   (Followers: 5, SJR: 6.469, h-index: 114)
Biologie in Unserer Zeit (Biuz)     Hybrid Journal   (Followers: 41, SJR: 0.12, h-index: 1)
Biology of the Cell     Full-text available via subscription   (Followers: 9, SJR: 1.812, h-index: 69)
Biomedical Chromatography     Hybrid Journal   (Followers: 7, SJR: 0.572, h-index: 49)
Biometrical J.     Hybrid Journal   (Followers: 5, SJR: 0.784, h-index: 44)
Biometrics     Hybrid Journal   (Followers: 37, SJR: 1.906, h-index: 96)
Biopharmaceutics and Drug Disposition     Hybrid Journal   (Followers: 10, SJR: 0.715, h-index: 44)
Biopolymers     Hybrid Journal   (Followers: 18, SJR: 1.199, h-index: 104)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44, SJR: 0.415, h-index: 55)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 161, SJR: 1.633, h-index: 146)
Biotechnology J.     Hybrid Journal   (Followers: 15, SJR: 1.185, h-index: 51)
Biotechnology Progress     Hybrid Journal   (Followers: 39, SJR: 0.736, h-index: 101)
Biotropica     Hybrid Journal   (Followers: 20, SJR: 1.374, h-index: 71)
Bipolar Disorders     Hybrid Journal   (Followers: 9, SJR: 2.592, h-index: 100)
Birth     Hybrid Journal   (Followers: 38, SJR: 0.763, h-index: 64)
Birth Defects Research Part A : Clinical and Molecular Teratology     Hybrid Journal   (Followers: 2, SJR: 0.727, h-index: 77)
Birth Defects Research Part B: Developmental and Reproductive Toxicology     Hybrid Journal   (Followers: 8, SJR: 0.468, h-index: 47)
Birth Defects Research Part C : Embryo Today : Reviews     Hybrid Journal   (SJR: 1.513, h-index: 55)

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Journal Cover Advanced Optical Materials
  [SJR: 2.488]   [H-I: 21]   [7 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Online) 2195-1071
   Published by John Wiley and Sons Homepage  [1597 journals]
  • Second-Harmonic Spectroscopy for Defects Engineering Monitoring in
           Transition Metal Dichalcogenides
    • Authors: Henrique G. Rosa; Lu Junpeng, Lídia C. Gomes, Manuel J. L. F. Rodrigues, Sow Chorng Haur, José C. V. Gomes
      Abstract: Defects engineering in transition metal dichalcogenides is a topic of intense research recently, since crystal properties can be controlled and tailored during and after fabrication. In this context, defects characterization is key to understand the material structure and enable specific applications. In this work, second-harmonic generation (SHG) spectroscopy is used to map concentric triangular defective regions in as-grown monolayer tungsten disulfide, demonstrating that SHG can be used for defects observation and characterization in layered noncentrosymmetric nanomaterials. In monolayer tungsten disulfide, in regions where sulfur atoms are replaced by vacancies, it is observed that the SHG signal experiences an enhancement of two orders of magnitude due to the presence of mid-gap states. Moreover, SHG is anticorrelated with photoluminescence emission from the material, showing that both techniques can provide complementary information about the crystalline structure. In comparison with other optical characterization techniques, SHG provides fast response, does not depend on real energy transitions, and can be used for defects mapping in several other materials regardless the optical bandgap energy.In this work, second-harmonic generation (SHG) spectroscopy is used to map concentric defective patterns in monolayer WS2 flakes. It was observed that the SHG signal is enhanced up to two orders of magnitude in areas within the material where defects are present (sulfur atoms are replaced by vacancies). These results provide important information towards defects engineering for nonlinear optical signals enhancement.
      PubDate: 2018-01-11T12:35:41.733185-05:
      DOI: 10.1002/adom.201701327
  • Moiré Metamaterials and Metasurfaces
    • Authors: Zilong Wu; Yuebing Zheng
      Abstract: Optical metamaterials and metasurfaces enable versatile light manipulations. Advancements in modeling, nanofabrication, and characterization tools have led to the development of metamaterials and metasurfaces for many applications: energy conversion, biomedicine, and information technology. Recently, metamaterials and metasurfaces with moiré configurations have attracted strong interest due to their highly tunable optical responses and high-throughput fabrication. Herein, state-of-the-art moiré metamaterials and metasurfaces are reviewed. The presentation covers fabrication techniques, structure–property relationships, and applications in lasing and biomedical sensing. The review concludes with challenges and opportunities for moiré metamaterials and metasurfaces.This review is focused on moiré metamaterials and metasurfaces. The fabrication techniques, optical properties, and applications of the moiré metamaterials and metasurfaces are covered, along with the authors' perspectives on challenges and future opportunities of this emerging field.
      PubDate: 2018-01-09T05:31:57.592766-05:
      DOI: 10.1002/adom.201701057
  • Excitations Partition into Two Distinct Populations in Bulk Perovskites
    • Authors: Lili Wang; Nicholas P. Brawand, Márton Vörös, Peter D. Dahlberg, John P. Otto, Nicholas E. Williams, David M. Tiede, Giulia Galli, Gregory S. Engel
      Abstract: Organolead halide perovskites convert optical excitations to charge carriers with remarkable efficiency in optoelectronic devices. Previous research predominantly documents dynamics in perovskite thin films; however, extensive disorder in this platform may obscure the observed carrier dynamics. Here, carrier dynamics in perovskite single-domain single crystals is examined by performing transient absorption spectroscopy in a transmissive geometry. Two distinct sets of carrier populations that coexist at the same radiation fluence, but display different decay dynamics, are observed: one dominated by second-order recombination and the other by third-order recombination. Based on ab initio simulations, this observation is found to be most consistent with the hypothesis that free carriers and localized carriers coexist due to polaron formation. The calculations suggest that polarons will form in both CH3NH3PbBr3 and CH3NH3PbI3 crystals, but that they are more pronounced in CH3NH3PbBr3. Single-crystal CH3NH3PbBr3 could represent the key to understanding the impact of polarons on the transport properties of perovskite optoelectronic devices.Transient absorption spectroscopy on perovskite single-domain single crystals reveals excitations partition into two distinct sets of carrier populations that coexist at the same radiation fluence, but decay differently. Ab initio calculations suggest that this observation is best explained by the coexistence of free carriers and localized carriers due to polaron formation.
      PubDate: 2018-01-09T05:31:22.311511-05:
      DOI: 10.1002/adom.201700975
  • Controlled Assembly of Organic Composite Microdisk/Microwire
           Heterostructures for Output Coupling of Dual-Color Lasers
    • Authors: Sufang Han; Wei Zhang, Bing Qiu, Haiyun Dong, Wenjie Chen, Manman Chu, Yingying Liu, Xinzheng Yang, Fengqin Hu, Yong Sheng Zhao
      Abstract: Dual-color lasing generated and outcoupled controllably at microscale is crucial for the realization of highly integrated photonic devices. This work constructs a type of organic microdisk/microwire dual-color laser heterostructures via a step-by-step directed molecular assembly strategy based on hydrogen-bond-assisted facet-selective growth mechanism. The microdisk therein can act as high-quality whispering-gallery-mode microcavity for blue lasing, while the interconnected wire functions as the Fabry–Pérot resonator to deliver green lasing. Moreover, the blue/green dual-color lasing is simultaneously generated and controllably outcoupled from the tip of the wire, which provides a proof-of-concept trial for the flexible integration of microlasers with different wavelengths toward multiband photonic circuits.Organic microdisk/microwire heterostructures are rationally constructed via a step-by-step directed molecular assembly of two kinds of organic laser dyes, which are used for the simultaneous generation and effective outcoupling of blue/green dual-color microscale lasers. The results provide a proof-of-concept trial for the flexible integration of microlasers toward multiband photonic circuits.
      PubDate: 2018-01-09T05:25:52.016329-05:
      DOI: 10.1002/adom.201701077
  • Polarization-Sensitive Structural Colors with Hue-and-Saturation Tuning
           Based on All-Dielectric Nanopixels
    • Authors: Bo Yang; Wenwei Liu, Zhancheng Li, Hua Cheng, Shuqi Chen, Jianguo Tian
      Abstract: Structural colors generated by the plasmonic resonance of metallic nanostructures, particularly aluminum, have been intensively studied in recent years. However, the inherent Ohmic loss and interband transitions in metals hinder the high efficiency and narrow bandwidth required for pure colors. Here, arrays of asymmetric titanium oxide elliptical nanopixels on a silica substrate are utilized to realize polarization-sensitive structural colors with high saturation, high efficiency (more than 90%), and high resolution. Owing to Fano resonance resulting from the interference between the radiating waves of dipole resonances and directly reflected waves, perfect narrow reflected spectra can be formed with nearly ideal efficiency in the visible spectrum based on this all-dielectric nanostructure. In particular, hue- and saturation-tuned colors can be simultaneously obtained under two orthogonally polarized incident lights with apparent color contrast. Based on the superior properties of the titanium oxide metasurface, the proposed design strategy is anticipated to form a new paradigm for practical applications, such as high-density optical data storage, nanoscale optical elements, sensing, security, and so on.The structural colors generated from asymmetric TiO2 nanopillars can exhibit three high-purity primary colors with efficiency of more than 90%. Moreover, by meticulous tuning of the geometrical parameters, RGB color switching can be obtained under two polarization states. Hue- and saturation-tuned structural colors are simultaneously realized upon utilizing the all-dielectric metasurface with varying periods under two orthogonally polarized incident lights.
      PubDate: 2018-01-09T03:12:11.649592-05:
      DOI: 10.1002/adom.201701009
  • Polarization Photoelectric Conversion in Layered GeS
    • Authors: Hung-Chung Hsueh; Jia-Xuan Li, Ching-Hwa Ho
      Abstract: Polarization photovoltaic effect is a unique character for an energy material with specific in-plane anisotropy. Especially, if the energy material has a direct bandgap close to 1.6 eV, it will efficiently absorb full sunlight spectrum with specific axial polarization. In this study, polarized microtransmittance measurements of GeS multilayer with polarization angles ranging from θ = 0° (E a) [through 90° (E b)] to θ = 180° (E a) have been studied near band edge. The polarized absorption edge follows a sinusoidal variation of E(θ) = 1.6 + 0.05⋅ sin(θ) eV with respect to the angle change of the polarized absorption spectra. This anisotropic optical response is well reproduced by first-principles calculations based on a combined Green's function technique, the GW–Bethe–Salpeter equation (BSE) approach. To characterize highly anisotropic band structure of layered GeS, polarized thermoreflectance measurement and first-principles quasiparticle band-structure calculations are also carried out. The interband transitions belonging to E a and E b polarizations are respectively identified. The polarized surface photovoltaic effects of a GeS Schottky solar cell are also tested. The special in-plane optical anisotropy (along a and perpendicular to the a axis) renders GeS owning highly bi-axial responsivity with respect to the c-plane photoelectric conversion.Polarization-dependent absorption edge and energy band for the GeS multilayer with polarization angles ranging from θ = 0° (E a) [through 90° (E b)] to θ = 180° (E a) are studied. The surface photovoltaic responses of a Cu–GeS Schottky solar cell with E a and E ⊥ a polarizations also show in-plane anisotropic photoresponsivities.
      PubDate: 2018-01-09T03:11:43.409691-05:
      DOI: 10.1002/adom.201701194
  • Trapped-Electron-Induced Hole Injection in Perovskite Photodetector with
           Controllable Gain
    • Authors: Dezhong Zhang; Chunyu Liu, Kanzhe Li, Wenbin Guo, Fengli Gao, Jingran Zhou, Xindong Zhang, Shengping Ruan
      Abstract: Perovskite is an excellent photosensitive material but it exhibits a shortcoming in providing photoconductive gain for layered photodetectors due to lacking of trap states. Here, the perovskite photodetectors are fabricated with controllable photoconductive gain by designing a trapped-electron-induced hole injection structure of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM):2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ)/Bathocuproine/Au. The deep trap states provided by F4-TCNQ can capture the photogenerated electrons from perovskite, which makes the hole injection barrier thin enough to be tunneled through, allowing the hole injection and forming a gain. Meanwhile, the gain is controllable by adjusting the electron trapping and hole transport capacities of PCBM:F4-TCNQ dual-functional layer, concomitantly realizing the transition of device from photovoltaic to photoconductive. Thus fabricated device achieves a higher external quantum efficiency of 6 × 104% at a lower bias of −1 V, and simultaneously maintains the rectifying behavior in dark, providing the detectivity of about 1 × 1015 Jones.A perovskite photodetector with controllable photoconductive gain is successfully designed and fabricated in this work. The 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) incorporated into [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) layer can trap electrons by the deep-lying energy level and then induce hole injection. Eventually, a high external quantum efficiency (EQE) of 6 × 104% is achieved at a low reverse bias of −1 V.
      PubDate: 2018-01-09T02:51:55.773674-05:
      DOI: 10.1002/adom.201701189
  • High-Performance All-Aryl Phenazasilines via Metal-Free Radical-Mediated
           CH Silylation for Organic Light-Emitting Diodes
    • Authors: Shen Xu; Huanhuan Li, Runfeng Chen, Zhicai Chen, Lijia Xu, Yuting Tang, Wei Huang
      Abstract: Heteroatom-containing organic molecules show a unique combination of properties for high-performance optoelectronic applications. With both Si and N heteroatoms in an aromatic architecture, phenazasilines are promising for optoelectronic devices, except for their synthetic difficulties. Through a newly developed two-step SiH/CH coupling silylation in a metal-free intramolecular radical-mediated catalysis mechanism, all-aryl phenazasilines that can be hardly synthesized by previous methods are facilely prepared and found to have excellent optoelectronic properties with both high thermal stability and high solubility due to the effects of bulky diphenyl substituents on Si, which cannot only strengthen the intramolecular interactions but also alleviate the intermolecular packing of phenazasilines. Using these compounds as host materials, high device performance was achieved with external quantum efficiency up to 21.3% and very low efficiency roll-off (1.4% at 1000 cd m−2), which are among the best of the recent reported results of blue phosphorescent organic light emitting diodes. This design strategy featuring rigid all-aryl phenazasiline motifs and the metal-free radical-catalyzed synthetic methodology should be important in developing high-performance multiheteroatom modified aromatic molecules for organic optoelectronics.All-aryl phenazasilines with embedded azasiline and diphenyl substituent are designed and facilely prepared by an efficient metal-free radical-mediated SiH/CH coupling method. Due to the combined effects of multiheteroatom incorporation and bulky aromatic substitution, the all-aryl phenazasilines show excellent properties for host materials of blue OLEDs, exhibiting high EQEs up to 21.3% and low roll-off of 1.4% at 1000 cd m−2.
      PubDate: 2018-01-09T02:40:47.609486-05:
      DOI: 10.1002/adom.201701105
  • Single-Shot Laser Additive Manufacturing of High Fill-Factor Microlens
    • Authors: Salvatore Surdo; Riccardo Carzino, Alberto Diaspro, Martí Duocastella
      Abstract: High fill-factor microlens arrays (MLA) are key for improving photon collection efficiency in light-sensitive devices. Although several techniques are now capable of producing high-quality MLA, they can be limited in fill-factor, precision, the range of suitable substrates, or the possibility to generate arbitrary arrays. Here, a novel additive direct-write method for rapid and customized fabrication of high fill-factor MLA over a variety of substrates is demonstrated. This approach uses a single laser pulse to delaminate and catapult a polymeric microdisc from a film onto a substrate of interest. Following a thermal reflow process, the printed disc can be converted into a planoconvex microlens offering excellent sphericity and high smoothness (RRMS < 40 Å). Importantly, the transfer of solid microdiscs enables fill-factors close to 100%, not achievable with standard direct-write methods such as inkjet printing or microdispensing. Arbitrary generation of MLA over flexible and curved surfaces, with microlenses presenting a curvature ranging from 20 to 240 µm and diffraction-limited performance, is demonstrated. The ease of implementation and versatility of the approach, combined with its potential parallelization, paves the way for the high-throughput fabrication of tailored MLA directly on top of functional devices.A novel laser additive manufacturing technique based on single-shot laser printing of polymeric discs followed by thermal reflow is presented. The method enables high-throughput fabrication of customizable microlens arrays with diffraction-limited performance and a fill-factor close to 100% directly on a variety of functional substrates including rigid, flexible, and curved.
      PubDate: 2018-01-08T05:42:01.181759-05:
      DOI: 10.1002/adom.201701190
  • Resonance Energy Transfer: Utilizing HomoFRET to Extend DNA-Scaffolded
           Photonic Networks and Increase Light-Harvesting Capability (Advanced
           Optical Materials 1/2018)
    • Authors: William P. Klein; Sebastián A. Díaz, Susan Buckhout-White, Joseph S. Melinger, Paul D. Cunningham, Ellen R. Goldman, Mario G. Ancona, Wan Kuang, Igor L. Medintz
      Abstract: The image depicts a DNA dendrimer displaying multiple copies of sequential pendant dyes throughout its structure. The dyes harvest light energy and direct it to a central focus using a dense Förster resonance energy transfer (FRET) network. Incorporation of extended homoFRET sections increases both the antenna gain and distance over which light can be propagated in this manner. This is reported by Igor L. Medintz and co-workers in article number 1700679.
      PubDate: 2018-01-04T15:23:30.270997-05:
      DOI: 10.1002/adom.201870005
  • Masthead: (Advanced Optical Materials 1/2018)
    • PubDate: 2018-01-04T15:23:29.477224-05:
      DOI: 10.1002/adom.201870004
  • Advanced Optical Materials: Shedding Light on Excellent Research for 5
    • Authors: Jos Lenders; Peter Gregory, Heike Höpcke, Ying Jia, Duoduo Liang, Richard Murray, Katja Paff, Jipei Yuan
      PubDate: 2018-01-04T15:23:28.93256-05:0
      DOI: 10.1002/adom.201701288
  • Cholesteric Liquid Crystals: Through the Spherical Looking-Glass:
           Asymmetry Enables Multicolored Internal Reflection in Cholesteric Liquid
           Crystal Shells (Advanced Optical Materials 1/2018)
    • Authors: Yong Geng; Ju-Hyun Jang, Kyung-Gyu Noh, JungHyun Noh, Jan P. F. Lagerwall, Soo-Young Park
      Abstract: In article number 1700923, Jan P. F. Lagerwall, Soo-Young Park, and co-workers show that the cholesteric shells in a microfluidics produced double emulsion enable a sequence of internal reflections if the shells have sufficiently thin top and thick bottom. While such asymmetry is promoted by buoyancy when the internal droplet has lower density than the liquid crystal, the elasticity of the cholesteric helix prefers a symmetric shell geometry, acting against gravity. This subtle balance can hide the internal reflections for long time.
      PubDate: 2018-01-04T15:23:27.115991-05:
      DOI: 10.1002/adom.201870002
  • Light-Emitting Coatings: Flexible and Adaptable Light-Emitting Coatings
           for Arbitrary Metal Surfaces based on Optical Tamm Mode Coupling (Advanced
           Optical Materials 1/2018)
    • Authors: Alberto Jiménez-Solano; Juan F. Galisteo-López, Hernán Míguez
      Abstract: Control over the photoluminescence spectrum, intensity, decay dynamics and direction is attained from several square centimetres large areas of a monolayer of nanoemitters embedded in a flexible multilayer mirror that is attached to the surface of a metal, as a result of the coupling between emission and Tamm plasmon modes. This is reported by Alberto Jiménez-Solano, Juan F. Galisteo-López, and Hernán Míguez in article number 1700560.
      PubDate: 2018-01-04T15:23:25.271506-05:
      DOI: 10.1002/adom.201870001
  • An Electrically Tunable Terahertz Plasmonic Device Based on Shape Memory
           Alloys and Liquid Metals
    • Authors: Hui Zhou; Ting Zhang, Sivaraman Guruswamy, Ajay Nahata
      Abstract: An electrically tunable terahertz (THz) plasmonic device is designed and fabricated using liquid metals (eutectic gallium indium) and shape memory alloy wires (Flexinol). The liquid metal is injected into the voids of a poly(dimethyl) siloxane microfluidic mold forming a periodic array of subwavelength apertures, while the wires are inserted into the elastomer below the metal plane. When a DC voltage is applied to the wires, they contract via Joule heating, reducing the aperture periodicity and blueshifting the transmission resonances of the device. When the voltage is removed, the wires cool and elongate back to their original length, allowing the transmission spectrum to return to its original state. The magnitude of this change depends upon the applied voltage. The device is shown to thermally cycle between the relaxed state and the fully contracted state reproducibly over at least 500 thermal cycles. The asymmetric geometry of the device and the contraction process yield transmission properties that are unexpected: two closely spaced resonances, where both resonances correspond to the same scattering indices, and an increase in the transmission amplitude of the lowest order resonance upon contraction. Numerical simulations are used to understand these features.An electrically tunable terahertz (THz) plasmonic device is designed and fabricated using liquid metals (eutectic gallium indium) and shape memory alloy wires (Flexinol). The application and removal of a DC voltage cause the wires to contract and elongate back to the original state, respectively, corresponding to tuning of the transmission resonances of the THz plasmonic device.
      PubDate: 2018-01-04T03:16:31.777918-05:
      DOI: 10.1002/adom.201700684
  • Propagation Loss-Immune Biocompatible Nanodiamond Refractive Index Sensors
    • Authors: Roman Shugayev; Peter Bermel
      Abstract: Propagation loss is a key impeding parameter affecting accuracy, range, and applicability of fluorescent microscopy techniques. In this work, a new nanophotonic platform for propagation loss mitigated fluorescent imaging using lifetime ratiometric measurement is proposed. By applying this methodology to local parameter sensing, a method for high sensitivity local refractive index measurement via lifetime/energy monitoring of fluorescent crystal color centers is numerically demonstrated. As the base of this platform, biocompatible diamond nanodisk structures are investigated that enable sensitive, propagation loss-immune monitoring of refractive index changes both in vitro and in vivo.Propagation loss is a key impeding parameter affecting accuracy, range, and applicability of fluorescent microscopy techniques. In this work, a new nanophotonic platform is proposed for propagation loss mitigated fluorescent imaging using lifetime ratiometric measurement. As the base of this platform, diamond color center nanodisk structures that enable sensitive, propagation loss-immune monitoring of refractive index changes both in vitro and in vivo are investigated.
      PubDate: 2018-01-04T03:16:12.709675-05:
      DOI: 10.1002/adom.201700487
  • Systematic Optical Design of Constituting Layers to Realize
           High-Performance Red-Selective Thin-Film Organic Photodiodes
    • Authors: Seongwon Yoon; Chang Woo Koh, Han Young Woo, Dae Sung Chung
      Abstract: A high-performance red-selective thin-film organic photodiode (OPD) is designed. Dual-band absorbing poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole)] (PPDT2FBT) is introduced as the photoactive donor layer of a planar heterojunction OPD in conjunction with a sol–gel synthesized ZnO acceptor layer. The active layer thickness is systematically controlled to suppress band II absorption (λmax = 420 nm) of PPDT2FBT without sacrificing band I absorption (λmax = 650 nm). The optimal PPDT2FBT thickness is 320 nm to realize red-selective absorption while maintaining the low dark current density of the OPD (predicted by optical simulation conducted using the transfer matrix method). In addition, the introduction of ZnO (with a strategically determined thickness) as an acceptor layer in front of PPDT2FBT in an illumination pathway enables further suppression of band II absorption because of the blue color filter effect. Consequently, the resulting OPD with a device architecture of indium tin oxide/ZnO/PPDT2FBT/MoO3/Ag shows an outstanding red-selective photodiode performance with peak detectivity up to 3.04 × 1012 Jones and a high linear dynamic range of 116 dB.A thin-film red-selective photodiode based on a planar heterojunction of poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole)] (PPDT2FBT) and ZnO is reported via optical manipulation. By independently optimizing the thicknesses of the PPDT2FBT and ZnO layers, not only extraction of highly red-selective photocurrent, but also suppression of unwanted dark current injection is realized, leading to peak detectivity up to 3.04 × 1012 Jones with narrow full width at half maximum of 138 nm.
      PubDate: 2018-01-04T03:15:27.566889-05:
      DOI: 10.1002/adom.201701085
  • Red, Green, and Blue Reflections Enabled in an Electrically Tunable
           Helical Superstructure
    • Authors: Yu-Cheng Hsiao; Zong-Han Yang, Dong Shen, Wei Lee
      Abstract: Materials with tunable optical properties in the visible spectrum are intriguingly important in science and technology. Such desired tunability can be conveniently accomplished by controlling optical materials with electric field. Now an organic film of self-organized helical superstructure producing electrically tunable reflection of visible light is introduced in this work. The composite is a dual-frequency thermosensitive cholesteric (DFTC) material consisting of a liquid crystal host doped with a binary chiral-dopant mixture including a thermosensitive chiral switch. The red, green, and blue reflections in the DFTC film can be obtained by varying the frequencies of a 45 Vrms applied voltage to induce dielectric heating. The resulting variation in temperature and, in turn, in helical pitch length, enables various wavelengths of reflection to render full-color display in a single film without the need of film stacking. As far as it is known, this is the first work to demonstrate broad electrical tuning of cholesteric reflection in red, green, and blue.Tunable optical materials are one of the hot topics in recent years. The most convenient way to control optical material properties is by applying an electric field. Here it is proposed to regulate the electric-field-induced color change from a self-organized organic superstructure by the dielectric heating effect. The tuning range spans the visible spectrum from blue to red.
      PubDate: 2018-01-04T03:10:51.331899-05:
      DOI: 10.1002/adom.201701128
  • Selective Diffraction with Complex Amplitude Modulation by Dielectric
    • Authors: Xu Song; Lingling Huang, Chengchun Tang, Junjie Li, Xiaowei Li, Juan Liu, Yongtian Wang, Thomas Zentgraf
      Abstract: Metasurfaces have attracted extensive interest due to their ability to locally manipulate optical parameters of light and easy integration to complex optical systems. Particularly, metasurfaces can provide a novel platform for splitting and diffracting light into several beams with desired profile, which is in contrast to traditional gratings. Here, a novel method for generating independently selective diffraction orders is proposed and demonstrated. This method is based on complex amplitude modulation with ultrathin dielectric metasurfaces. By tailoring the geometric parameters of silicon nanofin structures, the geometric and dynamic phase as well as the amplitude simultaneously can be controlled spatially. The results are compared with a metasurface that uses a phase-only modulation, to verify such selective diffraction can be solely efficiently achieved with complex amplitude modulation. Besides, the diffraction angles of each order have been measured, which are consistent with standard grating theory. The method developed for achieving selective diffraction with metasurfaces has potential applications in beam shaping, parallel laser fabrication, and nanoscale optical detection.A novel method for generating independently selective diffraction orders is proposed and experimentally demonstrated with ultrathin dielectric metasurfaces. By tailoring the geometric parameters and orientation angles of silicon nanofins, phase and amplitude are spatially controlled simultaneously. The developed method has potential applications in beam shaping, parallel laser fabrication, and nanoscale optical detection.
      PubDate: 2018-01-04T03:06:06.296931-05:
      DOI: 10.1002/adom.201701181
  • Generating Focused 3D Perfect Vortex Beams By Plasmonic Metasurfaces
    • Authors: Yuchao Zhang; Weiwei Liu, Jie Gao, Xiaodong Yang
      Abstract: Perfect vortex (PV) beams possessing annular intensity profiles independent of topological charges promise significant advances in particle manipulation, fiber communication, and quantum optics. The PV beam is typically generated from the Fourier transformation of the Bessel–Gauss beam. However, the conventional method to produce PV beams requires a series of bulky optical components, which greatly increases the system complexity and also hinders the photonic device integration. Here, plasmonic metasurfaces made of rectangular-hole nanoantennas as integrated beam converters are designed and demonstrated to generate focused 3D PV beams in a broad wavelength range, by combining the phase profiles of axicon, spiral phase plate, and Fourier transform lens simultaneously based on the Pancharatnam–Berry phase. It is demonstrated that the PV beam structures can be adjusted by varying several control parameters in the metasurface design. Moreover, multiple PV beams with arbitrary arrangement and topological charges are also produced. These results have the promising potential for enabling new types of compact optical devices for tailoring complex light beams and advancing metasurface-based functional integrated photonic chips.Focused 3D perfect vortex beams are generated by using compact metasurface beam converters, where the phase profiles of axicon, spiral phase plate, and Fourier transform lens are combined at the same time. The perfect vortex beam structures can be adjusted by the metasurface control parameters. Multiple perfect vortex arrays are also produced.
      PubDate: 2018-01-04T03:01:02.388919-05:
      DOI: 10.1002/adom.201701228
  • Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic
    • Authors: Chamika Hippola; Rajiv Kaudal, Eeshita Manna, Teng Xiao, Akshit Peer, Rana Biswas, Warren Dennis Slafer, Tom Trovato, Joseph Shinar, Ruth Shinar
      Abstract: A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor ηout, which is typically 2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning ηout ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed for blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost-effectively by direct room-temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome-shaped convex nanopatterns with height of ∼280–400 nm and pitch ∼750–800 nm were found to be optimal. Substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs.Strong light extraction from phosphorescent organic light-emitting diodes (PhOLEDs) fabricated on corrugated polycarbonate with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate anode is demonstrated. The external quantum efficiency (EQE) reaches 50%, 2.6× that on glass/ITO. (a) 10 × 10 μm2 polycarbonate substrate image; corrugation height ∼320 nm, pitch ∼750 nm. (b) Focused ion beam image of OLED fabricated conformally on corrugated plastic. (c) Green PhOLEDs' EQE versus brightness.
      PubDate: 2018-01-04T02:56:04.910008-05:
      DOI: 10.1002/adom.201701244
  • Multiwavelength Surface-Enhanced Raman Spectroscopy Using Rainbow Trapping
           in Width-Graded Plasmonic Gratings
    • Authors: Nastaran Kazemi-Zanjani; Moein Shayegannia, Rajiv Prinja, Arthur O. Montazeri, Aliakbar Mohammadzadeh, Katelyn Dixon, Siqi Zhu, Ponnambalam R. Selvaganapathy, Anna Zavodni, Naomi Matsuura, Nazir P. Kherani
      Abstract: Plasmonic gratings of rectangular groove profile with gradient in the groove width perform as unique surface-enhanced Raman spectroscopy (SERS) substrates by simultaneously confining multiple laser wavelengths proximally and inside their rectangular nanotrenches. These gratings consist of a metal–insulator–metal (MIM) groove of 40 nm width at the center, surrounded by grooves with widths increasing in 10 nm steps to a maximum of 180 nm. It is experimentally shown and theoretically confirmed that upon illumination a maximally enhanced electromagnetic field is generated at the center of these gratings as a result of plasmonic light trapping as well as waveguiding produced by the surrounding grooves. SERS enhancement factors of 106–107 are demonstrated for 20 μL min−1 flow of 1 × 10−3m aqueous phospholipid solution using 532, 638, and 785 nm laser illumination of the gratings integrated within microfluidic devices. These robust multiwavelength SERS substrates offer highly reproducible plasmonic field enhancement that can be tuned to cover broad wavelength ranges within the visible and near-infrared regime and are ideal for static and dynamic characterization of low concentration species. Further, the multispectral characteristic of these gratings facilitates multiplexing through various laser wavelengths thereby making it possible to readily access weak or silent Raman modes.Plasmonic gratings of rectangular groove profile with gradient in the groove width perform as unique surface-enhanced Raman spectroscopy substrates by simultaneously confining multiple laser wavelengths inside their rectangular nanotrenches. These gratings consist of a metal–insulator–metal (MIM) groove of 40 nm width at the center, surrounded by MIM grooves with widths increasing in 10 nm steps to a maximum of 180 nm.
      PubDate: 2018-01-02T03:22:20.899202-05:
      DOI: 10.1002/adom.201701136
  • Highly Efficient Nonlinear Optical Conversion in Waveguiding GaSe
           Nanoribbons with Pump Pulses Down to a Femto-Joule Level
    • Authors: Feng Liao; Yu Wang, Tao Peng, Jian Peng, Zhaoqi Gu, Huakang Yu, Tao Chen, Jiaxin Yu, Fuxing Gu
      Abstract: Layered GaSe flakes have revealed strongest second-harmonic (SH) generation among all the two-dimensional (2D) atomic crystals measured up to now. However, the unique feature of physical atomic thickness at nanometer scale prevents their practical applications in efficient nonlinear optical conversion due to limited light–matter interaction length. In this work, high quality single-crystal GaSe nanoribbons (NRs) are fabricated and demonstrated as waveguides with good performance. By taking advantage of the strong confinement and long interaction length of the waveguiding approach, significantly enhanced nonlinear light–matter interaction is observed in GaSe NRs. Based on transverse SH generation, a single GaSe NR-configured optical auto-correlator is constructed for ultrashort pulse characterization. Because of the large second-order nonlinear susceptibility, high sensitivity down to few femto-joule (fJ) is realized. To the best of our knowledge, this is the highest energy sensitivity among the reported nanoscale auto-correlators. Such NR waveguides and devices are highly compatible with standard optical fiber systems. The presented results may enable the construction of future energy efficient nonlinear photonic circuitry, chips, and devices.Highly efficient frequency conversion in GaSe nanoribbons is demonstrated. Benefitting from the strong confinement of subwavelength optical guiding and high second-order nonlinearity of the GaSe material, here the fact is demonstrated that a single GaSe nanoribbon optical correlator for ultrashort pulse characterization with femto-joule-level input pulse energy has higher sensitivity than those reported before.
      PubDate: 2018-01-02T03:15:56.479485-05:
      DOI: 10.1002/adom.201701012
  • An All-Dielectric Metasurface Building Block for the Kerker Effect between
           Excitons and Nanocavities: Germanium Nanogroove
    • Authors: Yingcong Huang; Churong Ma, Jiahao Yan, Guowei Yang
      Abstract: Coupling between light and matter has many infusive physical effects and potential applications. Large Rabi splitting energy is achieved in many plasmonic nanostructures; however, these noble metallic materials generally suffer from a high level of Joule heating losses at optical frequencies. As an alternative strategy, all-dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all-dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove as a new all-dielectric metasurface building block is demonstrated for the Kerker effect between molecular excitons and nanocavities. A distinct dip in the backward scattering spectra is observed, indicating relatively strong light–matter interaction due to the cavity magnetic resonance mode in the grooves. Germanium with a large real part and nonnegligible imaginary part of the refractive index in the visible region provides magnetic field enhancement similar to that of other all-dielectric nanostructures; this phenomenon is theoretically explained by simulating the magnetic field distribution in the grooves. These findings may help researchers to better understand the interactions between all-dielectric nanostructures and molecular excitons and indicate that germanium nanogrooves can potentially be used as metasurface building blocks in nanophotonic devices.All-dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all-dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove is demonstrated as a new all-dielectric metasurface building block for the Kerker effect between molecular excitons and nanocavities.
      PubDate: 2017-12-29T03:37:04.296235-05:
      DOI: 10.1002/adom.201701176
  • Optical Detection and Spatial Modulation of Mid-Infrared Surface Plasmon
           Polaritons in a Highly Doped Semiconductor
    • Authors: Davide Maria Di Paola; Anton V. Velichko, Mario Bomers, Nilanthy Balakrishnan, Oleg Makarovsky, Mario Capizzi, Laurent Cerutti, Alexei N. Baranov, Manoj Kesaria, Anthony Krier, Thierry Taliercio, Amalia Patanè
      Abstract: Highly doped semiconductors (HDSCs) are promising candidates for plasmonic applications in the mid-infrared (MIR) spectral range. This work examines a recent addition to the HDSC family, the dilute nitride alloy In(AsN). Postgrowth hydrogenation of In(AsN) creates a highly conducting channel near the surface and a surface plasmon polariton detected by attenuated total reflection techniques. The suppression of plasmonic effects following a photoannealing of the semiconductor is attributed to the dissociation of the NH bond. This offers new routes for direct patterning of MIR plasmonic structures by laser writing.Mid-infrared surface plasmon polaritons are created in the highly H-doped In(AsN) semiconductor. The spatial modulation of the plasmon resonance is achieved by laser writing: the photon excitation tailors the chemical composition of the semiconductor by dissociation of the NH bond, thus offering a new route for plasmonic patterning in the mid-infrared spectral range.
      PubDate: 2017-12-28T05:33:35.468527-05:
      DOI: 10.1002/adom.201700492
  • Ultrastrong Coupling of Electrically Pumped Near-Infrared
           Exciton-Polaritons in High Mobility Polymers
    • Authors: Martin Held; Arko Graf, Yuriy Zakharko, Pengning Chao, Laura Tropf, Malte C. Gather, Jana Zaumseil
      Abstract: Exciton-polaritons are quasiparticles with hybrid light–matter properties that may be used in new optoelectronic devices. Here, electrically pumped ultrastrongly coupled exciton-polaritons in a high-mobility donor–acceptor copolymer are demonstrated by integrating a light-emitting field-effect transistor into a metal-clad microcavity. Near-infrared electroluminescence is emitted exclusively from the lower polariton branch, which indicates efficient relaxation. A coupling strength of 24% of the exciton transition energy implies the system is in the ultrastrong coupling regime with a narrow and almost angle-independent emission. The lower polariton energy, which can be adjusted by the cavity detuning, strongly influences the external quantum efficiency of the device. Driving the transistors at ambipolar current densities of up to 4000 A cm−2 does not decrease the coupling strength or polariton emission efficiency. Cavity-integrated light-emitting field-effect transistors thus represent a versatile platform for polariton emission and polaritonic devices.Ultrastrongly coupled near-infrared exciton-polaritons are electrically pumped by integrating a light-emitting transistor into an optical microcavity. The broad near-infrared emission spectrum of the uncoupled high-mobility polymer is significantly narrowed, while the dispersion is almost angle-independent with minimal energy-shift. Tuning the cavity changes the external quantum efficiency. The potential impact of the microcavity on charge transport is investigated.
      PubDate: 2017-12-28T05:27:46.017035-05:
      DOI: 10.1002/adom.201700962
  • High-Performance, Self-Driven Photodetector Based on Graphene Sandwiched
           GaSe/WS2 Heterojunction
    • Authors: Quanshan Lv; Faguang Yan, Xia Wei, Kaiyou Wang
      Abstract: Restacking the exfoliated 2D layered materials into complex heterostructures with new functionality has opened a new platform for materials engineering and device application. In this work, graphene sandwiched p-GaSe/n-WS2 vertical heterostructures are fabricated for photodetection. The devices show excellent performance on photodetection from ultraviolet to visible wavelength range, including high photoresponsivity (≈149 A W−1 at 410 nm), short response time of 37 µs, and self-powered photodetection. The scanning photocurrent microscopy is also employed to investigate the photocurrent generation in the heterojunction and a significant enhancement of the photoresponse is found in the overlapping region. The results suggest that the graphene sandwiched vertical heterojunctions are promising in future novel optoelectronic devices applications.A high-performance, self-driven photodetector based on GaSe/WS2 heterojunction is demonstrated. The graphene sandwiched vertical heterostructure exhibits excellent performance on photodetection from ultraviolet to visible wavelength with a high photoresponsivity of 149 A W−1, rapid response of 37 µs, and self-powered photodetection, showing great potential for future optoelectronics applications.
      PubDate: 2017-12-28T02:14:25.004534-05:
      DOI: 10.1002/adom.201700490
  • Functionalized Flexible Soft Polymer Optical Fibers for Laser
    • Authors: Nan Jiang; Rajib Ahmed, Ahmmed A. Rifat, Jingjing Guo, Yixia Yin, Yunuen Montelongo, Haider Butt, Ali K. Yetisen
      Abstract: Optical waveguides allow propagating light through biological tissue in optogenetics and photomedicine applications. However, achieving efficient light delivery to deep tissues for long-term implantation has been limited with solid-state optical fibers. Here, a method is created to rapidly fabricate flexible, functionalized soft polymer optical fibers (SPOFs) coupled with silica fibers. A step-index core/cladded poly(acrylamide-co-poly(ethylene glycol) diacrylate)/Ca alginate SPOF is fabricated through free-radical polymerization in a mold. The SPOF is integrated with a solid-state silica fiber coupler for efficient light delivery. The cladded SPOF shows ≈1.5-fold increase in light propagation compared to the noncladded fiber. The optical loss of the SPOF is measured as 0.6 dB cm−1 at the bending angle of 70° and 0.28 dB cm−1 through a phantom tissue. The SPOF (inner Ø = 200 µm) integrated with a 21 gauge needle (inner Ø = 514 µm) is inserted within a porcine tissue. The intensity of light decreases ≈60%, as the SPOF is implanted as deep as 2 cm. Doped with fluorescent dye and gold nanoparticles, the SPOF fiber exhibits yellow-red and red illumination. Living cells can also be incorporated within the SPOF with viability. The flexible SPOFs may have applications in photodynamic light therapy, optical biosensors, and photomedicine.Soft polymer optical fibers coupled with solid-state fibers are utilized for efficient light propagation within biological tissues. The step-index optical fibers have poly(acrylamide-co-poly(ethylene glycol) diacrylate) as cores, and calcium alginate as claddings. Polymer optical fibers are functionalized with fluorophores, nanoparticles, and living cells, which may allow clinical applications in laser photomedicine.
      PubDate: 2017-12-28T01:58:48.737543-05:
      DOI: 10.1002/adom.201701118
  • Novel Host Materials Based on Dibenzothiophene and Carbazolylcarbazole for
           Extended Lifetime in Blue Phosphorescent Organic Light-Emitting Diodes
    • Authors: Su Kyeong Shin; Sung Yong Byeon, Si Hyun Han, Jun Yeob Lee
      Abstract: High triplet energy materials based on dibenzothiophene and carbazolylcarbazole are developed as hosts for lifetime extension in blue phosphorescent organic light-emitting diodes. Two host materials with or without a biphenyl linker between dibenzothiophene and carbazolylcarbazole are synthesized to get insight about the effect of aromatic linkers on the photophysical properties of the hosts and the device performances of a blue triplet emitter doped phosphorescent organic light-emitting diodes. It is described that the host design with dibenzothiophene and carbazolylcarbazole at 4-position of dibenzothiophene is effective for both high efficiency and improved lifetime. In particular, the new hosts improved the lifetime of the blue devices by more than five times while enhancing the quantum efficiency compared to a common triplet host.New host materials with carbazolylcarbazole and dibenzothiophene groups are synthesized for blue phosphorescent organic light-emitting diodes (PhOLEDs). Biphenyl linker is applied to understand the effect of aromatic linkers on photophysical properties. As a result, those materials work as efficiency and long lifetime host materials for blue PhOLEDs and prolong the lifetime by more than fivefold compared with that of 1,3-bis(N-carbazolyl)benzene.
      PubDate: 2017-12-28T01:58:02.649033-05:
      DOI: 10.1002/adom.201701007
  • Lasing Characteristics of CH3NH3PbCl3 Single-Crystal Microcavities under
           Multiphoton Excitation
    • Authors: Decheng Yang; Chao Xie, Xuhui Xu, Peng You, Feng Yan, Siu Fung Yu
      Abstract: Photoluminescence of CH3NH3PbCl3 single crystals under multiphoton excitation is studied. The emission intensity and wavelength, which are related to the phase of the single crystals, are found to be dependent on the operating temperature and pressure. High optical gain (>110 cm−1 @ ≈395 nm) and high absorption coefficient (≈9 × 10−10 cm9 GW−5 @ 2400 nm) can also be obtained from the single crystals. With suitable design of the resonant optical amplification, lasing emission at ≈395 nm is demonstrated from the single-crystal microcavities under 2400 nm excitation. Hence, it is verified that CH3NH3PbCl3 single crystals can offer new opportunities for novel nonlinear photonics applications.The photoluminescence of CH3NH3PbCl3 microcrystals under single- and multiphoton excitation is studied. The emission intensity and wavelength are found to be dependent on the phase of the crystal and can be controlled by temperature and pressure. The microcrystal is a natural vertical cavity and can support lasing action in orthorhombic phase under multiphoton excitation.
      PubDate: 2017-12-28T01:57:44.090629-05:
      DOI: 10.1002/adom.201700992
  • Broadband Nonlinear Photoresponse of 2D TiS2 for Ultrashort Pulse
           Generation and All-Optical Thresholding Devices
    • Authors: Yanqi Ge; Zhengfeng Zhu, Yanhua Xu, Yunxiang Chen, Si Chen, Zhiming Liang, Yufeng Song, Yousheng Zou, Haibo Zeng, Shixiang Xu, Han Zhang, Dianyuan Fan
      Abstract: 2D titanium disulfide (TiS2) is recently found to have strong light absorption properties from visible to infrared (IR) region. This feature is highly attractive for applications in nonlinear photonics; however, the mechanism of broadband light–matter interaction is yet to be determined and nonlinear photonic devices are not developed. Here, for the first time, the experimental evidence supporting the mechanism of the broadband nonlinear photoresponse in ultrathin TiS2 nanosheets ranging from 400 nm to 1390 nm is reported through laser Z-scan measurements. High-performance nonlinear photonic devices operating in the telecommunication band are also demonstrated. A novel saturable absorber (SA) device is successfully fabricated based on a 2D TiS2-decorated fiber, which exhibits outstanding ultrashort pulse generation performance with pulse duration of ≈1.04 ps centered at 1569.5 nm. Furthermore, as a stable all-optical thresholding component, the device can effectively attenuate noise and boost the signal-to-noise ratio of the pulse from 1.90 to 10.68 dB. The findings indicate that TiS2-based SA devices can be developed into excellent highly nonlinear photonic devices, which may advance the development of TiS2-based optical communication technologies in the future.Ultrathin and uniform semimetallic titanium disulfide nanosheets are synthesized via a colloidal chemistry method. A Z-scan system is used to confirm their broadband nonlinear optical response from visible to mid-infrared wavelengths. Thus, TiS2 nanosheet-based optical devices exhibit excellent performance in mode-locked fiber lasers and all-optical thresholding components.
      PubDate: 2017-12-28T01:38:34.417894-05:
      DOI: 10.1002/adom.201701166
  • Thermo-optical Tunable Ultracompact Chip-Integrated 1D Photonic
           Topological Insulator
    • Authors: Chong Li; Xiaoyong Hu, Wei Gao, Yutian Ao, Saisai Chu, Hong Yang, Qihuang Gong
      Abstract: An on-chip integrated one-dimension topological insulator in the optical communication range is realized directly in an integrated photonic circuit. The system takes on a configuration of a 220 nm thick 1D photonic crystal heterostructure sandwiched between two gold films. A photonic topological edge state centered at 1550 nm is obtained for the chip-integrated one-dimension topological insulator made of a silicon/SiO2 photonic crystal heterostructure with a feature size of only 2.25 µm integrated with a silicon waveguide. On/off switching of the photonic topological edge state was also achieved in a 1D topological insulator made of a VO2/SiO2 photonic crystal heterostructure based on a thermally induced insulator-to-metal transition of VO2. This system not only paves the way for practical applications of photonic topological insulators in integrated photonic devices and chips but also provides a platform for fundamental studies of topological photonics.An on-chip integrated 1D topological insulator is realized directly in an integrated photonic circuit. A topological edge state centered at 1550 nm is obtained for the chip-integrated 1D topological insulator made of a silicon/SiO2 photonic crystal heterostructure. On/off switching of the photonic topological edge state is also achieved based on a thermally induced insulator-to-metal transition.
      PubDate: 2017-12-28T01:25:45.408795-05:
      DOI: 10.1002/adom.201701071
  • Room-Temperature Red–Green–Blue Whispering-Gallery Mode Lasing and
           White-Light Emission from Cesium Lead Halide Perovskite (CsPbX3, X = Cl,
           Br, I) Microstructures
    • Authors: Pengfei Guo; Mohammad Kamal Hossain, Xia Shen, Haibin Sun, Wenchao Yang, Chaoping Liu, Chun Yuen Ho, Cheuk Kai Kwok, Sai-Wing Tsang, Yongsong Luo, Johnny C. Ho, Kin Man Yu
      Abstract: Wavelength-tunable nano/microlasers are essential components for various highly integrated and multifunctional photonic devices. Based on the different band gap/composition of inorganic cesium lead halide perovskite materials, broad band light absorption and emission devices can be achieved. Herein, a vapor–liquid–solid route for growing cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) microcrystal structures is demonstrated. These square-shaped microstructures exhibit strong blue, green, and red photoluminescence, indicating that their band gaps can be engineered to cover the entire visible range. Optically pumped red–green–blue whispering-gallery mode lasers based on the controlled composition of these microcrystals are successfully realized at room temperature. Moreover, rationally designed white-light-emitting chips with high brightness are fabricated utilizing these metal halide perovskite microstructures grown on sapphire. All these results evidently suggest a feasible route to the design of red–green–blue lasers and white-light emitters for potential applications in full-color displays as well as photonic devices.Based on composition-tunable cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) microcrystal structures, broad-band light emission devices can be achieved. Room-temperature optically pumped red–green–blue whispering-gallery mode lasers as well as white-light emission are successfully realized.
      PubDate: 2017-12-27T03:09:08.926758-05:
      DOI: 10.1002/adom.201700993
  • Perovskite Excitonics: Primary Exciton Creation and Crossover from Free
           Carriers to a Secondary Exciton Phase
    • Authors: Valerio Sarritzu; Nicola Sestu, Daniela Marongiu, Xueqing Chang, Qingqian Wang, Maria Antonietta Loi, Francesco Quochi, Michele Saba, Andrea Mura, Giovanni Bongiovanni
      Abstract: Understanding exciton formation is of fundamental importance for emerging optoelectronic materials, like hybrid organic–inorganic perovskites, as excitons are the lowest-energy photoexcitations in semiconductors, are electrically neutral, and do not directly contribute to charge transport, but can emit light more efficiently than free carriers. However, despite the increasing attention toward these materials, experimental results on the processes of formation of an exciton population in perovskites are still elusive. Here, an ultrafast differential photoluminescence technique is presented that is able to track the kinetics of exciton formation and dissociation in CH3NH3PbBr3. Data show the presence of geminate excitons, i.e., primary excitons directly created upon photon absorption, and their dissociation into free electron–hole pairs. The formation is demonstrated of a secondary exciton phase through pairing of the initial population of free carriers. The analysis of the generation of secondary excitons provides an estimate of the Langevin factor, the parameter governing the charge-pairing rate. Understanding and controlling the formation of a bright exciton population instead of a highly conductive free carrier population may help to design new hybrid perovskite materials with tailored optoelectronic functionalities.Hybrid organic–inorganic lead halide perovskites operate in solar cells and light-emitting diodes (LEDs) as free carriers semiconductors, while excitons are elusive. Nonetheless here excitons are shown to form and even to overcome free carriers in number under appropriate conditions, possibly leading to more efficient light emission from lead halide perovskite materials designed ad hoc.
      PubDate: 2017-12-27T03:08:20.094364-05:
      DOI: 10.1002/adom.201700839
  • Giant Two-Photon Absorption in Mixed Halide Perovskite
           CH3NH3Pb0.75Sn0.25I3 Thin Films and Application to Photodetection at
           Optical Communication Wavelengths
    • Authors: Ying Xie; Jiandong Fan, Chong Liu, Shumeng Chi, Zeyan Wang, Haohai Yu, Huaijin Zhang, Yaohua Mai, Jiyang Wang
      Abstract: Photodetection in the optical communication wavelength band (OCWB) is a key technique for data processing communications. Photodetectors with integrability, ease of fabrication, low cost, and excellent detection properties are favorable for practical applications. Metal halide perovskite thin films have exhibited intriguing optoelectronic properties. However, their relatively wide intrinsic band gaps indicate that direct photodetection in the infrared OCWB seems impossible. Here, for the first time, direct infrared photodetection covering the OCWB with a metal halide perovskite is demonstrated. Associated with an Sn-component dependent band gap, a CH3NH3Pb0.75Sn0.25I3 perovskite thin film is fabricated, whose nonlinear two-photon absorption can expand the optical response up to 1.8 µm. Two-photon absorption is studied and a very large absorption coefficient of 1.15 cm kW−1 is measured, a value that is respectively 5 and 106 times larger than that of CH3NH3PbI3 thin films and halide perovskite bulk crystals. Based on this favorable performance, direct photodetection at 1535 nm in the C-band of the OCWB and at 1064 nm is characterized. The realization of direct infrared photodetection in a metal halide perovskite provides a possible alternative in advanced integrated optoelectronics and electronics.For the first time, giant two-photon absorption in mixed halide perovskite CH3NH3Pb0.75Sn0.25I3 thin films is reported. Taking advantage of two-photon absorption, the optical response can be expanded up to 1.8 µm and direct infrared photodetection covering the optical communication wavelength band is realized with halide perovskite as photodetector.
      PubDate: 2017-12-27T03:07:49.404999-05:
      DOI: 10.1002/adom.201700819
  • Trap Assisted Bulk Silicon Photodetector with High Photoconductive Gain,
           Low Noise, and Fast Response by Ag Hyperdoping
    • Authors: Xiaodong Qiu; Xuegong Yu, Shuai Yuan, Yuhan Gao, Xuemei Liu, Yang Xu, Deren Yang
      Abstract: Silicon-based photoconductors, with their low cost, high sensitivity, and complementary metal–oxide–semiconductor (CMOS) compatibility, have great potential for high-resolution imaging, light-activated switching, and single-photon counting. However, they usually suffer from a large dark leakage current and a long response time, which greatly limits their applications. Here, a high-performance bulk silicon photodetector is fabricated working at room temperature with a broad spectral response range from 300 to 1200 nm through silver (Ag) hyperdoping. The detector shows a low dark current of 3.8 × 10−7 A cm−2 and a high external quantum efficiency of 266.0% for 800 nm at −1 V reverse bias, indicating a photoconductive gain. Moreover, the Si:Ag photodetector has a very low noise and a high detectivity (≈1.84 × 1012 Jones at −1 V), and meanwhile exhibits a rapid response speed with the rise time of 12.5 µs and fall time of 15.9 µs. By combining with the deep level transient spectrum measurements, it is believed that the operating mechanism of the detector is based on the electron traps with an average energy level of Ec– 0.28 eV induced by the Ag hyperdoping. These results are of significance for the fabrication of silicon-based photodetectors with high performances.A high-performance bulk silicon photodetector with a large photoconductive gain and low noise current has been obtained through silver hyperdoping. The high gain is attributed to the electron traps with energy level of Ec – 0.28 eV, which assists the holes tunneling and injection from external circuit. These results are significant for the fabrication of silicon-based photodetectors with high performances.
      PubDate: 2017-12-27T03:07:20.304957-05:
      DOI: 10.1002/adom.201700638
  • Single Source Precursor Chemical Vapor Decomposition Method to Fabricate
           Stable, Bright Emissive Aluminum Hydroxide Phosphors for UV-Pumped White
           Light-Emitting Devices
    • Authors: Bingkun Chen; Xingjian Xu, Shuangyang Zou, Yongtian Wang, Bingsuo Zou, Haizheng Zhong, Andrey L. Rogach
      Abstract: Aluminum hydroxides are considered to be a potential abundant, low-cost blue emissive material to construct UV-pumped white light-emitting diodes (WLEDs). In this work, a single-source precursor chemical vapor decomposition method is adapted to fabricate stable, strongly emissive aluminum hydroxide phosphors with photoluminescence quantum yield of up to 69% in solid state by thermal decomposing aluminum diacetate hydroxide (Al(OH)(Ac)2) at temperatures (260–360 °C) in N2 atmosphere. It exhibits layered, amorphous structure and its emission of aluminum hydroxide is enhanced by electron-donating surface hydroxyl groups and originates from F+ centers and carbon-related defects contributing to UV (388 nm) and blue (450–520 nm) spectral regions, respectively. Employing the as-fabricated aluminum hydroxides as blue phosphor and CuInS2 nanocrystals as red phosphor, high color rendering and high-efficiency WLEDs with luminous efficiencies up to 37 lm W−1 and high color rendering index of 91 are fabricated. This is the best performance reported so far for aluminum hydroxide based LEDs.Highly blue emissive aluminum hydroxide phosphor with photoluminescence quantum yield up to 69% is fabricated by a single-source precursor chemical vapor decomposition strategy. Blue UV-pumped light-emitting diodes (LEDs) based on the aluminum hydroxide phosphor reach luminous efficiency up to 37 lm W−1, while UV–white LEDs integrating blue-emitting aluminum hydroxide and red-emitting CuInS2 NCs achieve high color rendering index values of 91.
      PubDate: 2017-12-27T03:02:56.424473-05:
      DOI: 10.1002/adom.201701115
  • Magnetochromic Photonic Hydrogel for an Alternating Magnetic
           Field-Responsive Color Display
    • Authors: Wentao Wang; Xiaoqiao Fan, Feihu Li, Jinjing Qiu, Malik Muhammad Umair, Wenchen Ren, Benzhi Ju, Shufen Zhang, Bingtao Tang
      Abstract: As an external stimulus for stimuli-responsive chromic materials, a magnetic field has the benefits of contactless control, instant action, and ease of integration into electronic devices. Hence, the development of a magnetically responsive photonic crystal provides a new platform for color displays. However, magnetically controlled display systems have been primarily limited to liquid systems of colloidal crystals; their application to solid chromic systems has been difficult because the ordered array structure is fixed by a polymer network. A novel solid magnetochromic photonic hydrogel is developed that enables colorimetric responses to an alternating magnetic field (AMF). This notable magnetochromic performance is attributed to the superior magnetothermal effect of 1D aggregates of magnetic chains fixed in a thermosensitive hydrogel. The AMF-responsive magnetic hydrogel exhibits excellent stability for repeated use. This study presents a basis for the development of responsive solid materials with new optical effects for future chromatic applications.A solid photonic hydrogel for a colorimetric response to an alternating magnetic field is developed through a rapid magnetically induced self-assembly of magnetic colloids followed by an instant UV curing process. The performance of this magnetochromic display is attributed to the superior magnetothermal effect of 1D aggregates of magnetic chains fixed in the thermosensitive hydrogel.
      PubDate: 2017-12-27T03:02:26.760195-05:
      DOI: 10.1002/adom.201701093
  • Dynamically Tunable Deep Subwavelength High-Order Anomalous Reflection
           Using Graphene Metasurfaces
    • Authors: Chao Wang; Wenwei Liu, Zhancheng Li, Hua Cheng, Zhi Li, Shuqi Chen, Jianguo Tian
      Abstract: Graphene-based metasurfaces have emerged as promising photoelectric devices that can dynamically control the behavior of electromagnetic waves. The high-order anomalous reflection provides an additional degree of freedom in the field of photonic research. Here, a series of gradient graphene metasurfaces with high-order modes to manipulate the wavefront of reflected light is proposed. By properly arranging the graphene nanostructures, 5-order anomalous reflection and 15-order high-quality Laguerre–Gaussian beams are achieved. Furthermore, the efficiency of the metasurfaces is dynamically controlled by tuning the electrostatic gating to change the Fermi energy of graphene. This work offers a new idea for the development of tunable wavefront-controlling devices and contributes to a wide range of applications in photonic systems.A series of gradient graphene metasurfaces with high-order modes can achieve deep subwavelength modulation in the infrared waveband. The 5-order anomalous reflection and 15-order high-quality Laguerre–Gaussian beams are achieved. Furthermore, the efficiency of the metasurfaces can be dynamically controlled by tuning the electrostatic gating to change the Fermi energy of graphene.
      PubDate: 2017-12-27T03:01:58.755858-05:
      DOI: 10.1002/adom.201701047
  • Potassium Ion Assisted Synthesis of Organic–Inorganic Hybrid Perovskite
           Nanobelts for Stable and Flexible Photodetectors
    • Authors: Bai-Sheng Zhu; Zhen He, Ji-Song Yao, Chen Chen, Kun-Hua Wang, Hong-Bin Yao, Jian-Wei Liu, Shu-Hong Yu
      Abstract: Low-dimensional organic–inorganic hybrid perovskites with controllable morphologies are attractive for high-performance optoelectronic devices. In particular, the 1D organic–inorganic hybrid perovskite nanowires/nanobelts are promising for flexible photodetectors due to high photoresponsivity and strain endurance capability. Herein, a novel and large-scale synthesis of (C4H9NH3)2PbBr4 organic–inorganic hybrid perovskite nanobelt achieved by the potassium ions assisted controllable crystal growth during the precipitation process in solutions is reported. The obtained (C4H9NH3)2PbBr4 perovskite nanobelts exhibit high-efficient photoluminescence and superior stability under ambient conditions. Furthermore, these nanobelts are used as photoresponsive materials to fabricate flexible photodetectors, which show much higher switching ratio than that of photodetectors based on (C4H9NH3)2PbBr4 microplatelets. Attractively, after repeated bending for 1000 times, the nanobelt-based photodetector only shows less than 10% decay in switching ratio in contrast to at least 40% of switching ratio decay for the microplatelets-based photodetector. The reported potassium ion assisted large-scale synthesis of (C4H9NH3)2PbBr4 nanobelts paves a new avenue for the application of organic–inorganic hybrid perovskites in flexible optoelectronic devices.Large-scale synthesis of (C4H9NH3)2PbBr4 perovskite nanobelts is achieved by the potassium ions assisted controllable crystal growth during the precipitation of perovskites in solutions. As-synthesized (C4H9NH3)2PbBr4 nanobelts are fabricated into flexible photodetectors, which show much higher switching ratio and better flexible capability than photodetectors based on (C4H9NH3)2PbBr4 microplatelets.
      PubDate: 2017-12-27T03:01:29.494947-05:
      DOI: 10.1002/adom.201701029
  • Enhanced Two-Photon-Pumped Emission from In Situ Synthesized Nonblinking
           CsPbBr3/SiO2 Nanocrystals with Excellent Stability
    • Authors: Zhiping Hu; Zhengzheng Liu, Yao Bian, Shiqi Li, Xiaosheng Tang, Juan Du, Zhigang Zang, Miao Zhou, Wei Hu, Yuxi Tian, Yuxin Leng
      Abstract: Perovskites have emerged as a class of cutting-edge photovoltaic and light-emitting materials. However, poor stability due to high moisture sensitivity and undesirable blinking severely limits their further application. Here, to solve these problems without destroying optoelectronic performance, a simple process for the fabrication of nonblinking CsPbBr3 quantum dots (QDs) is investigated. By embedding CsPbBr3 QDs into waterless silica spheres, the blinking of QDs can be strikingly suppressed, with an effective improvement of the moisture resistance and enhanced photostability. The silica sphere can also prevent anion exchange of different halide elements between perovskite QDs. Ultrastable amplified spontaneous emission (ASE) from QDs/SiO2 with no degradation for at least 12 h is observed under continuous laser irradiation (4 × 107 continuous intense laser shots), with almost no ASE degradation evident after 60 d of storage under ambient conditions. Most notably, the ASE threshold (Pth) of CsPbBr3 QDs is decreased by 50% and the relative efficiency increased by 388%. The perovskite QDs coated by the waterless SiO2 shell provide a novel platform for realizing perovskite nanomaterials with improved operational stability, nonblinking properties, and enhanced emission all at the same time, which is especially attractive for photovoltaic and light-emitting device applications.To enhance the stability of perovskite quantum dots, a silica sphere is used as a shell by in situ fabrication without water. The embedding of quantum dots in the silica sphere leads to the observation of enhanced amplified spontaneous emission under one- and two-photon excitation. Moreover, the blinking phenomenon characteristic of perovskite nanocrystals is also suppressed.
      PubDate: 2017-12-27T03:00:58.292215-05:
      DOI: 10.1002/adom.201700997
  • Tailorable Upconversion White Light Emission from Pr3+ Single-Doped Glass
           Ceramics via Simultaneous Dual-Lasers Excitation
    • Authors: Zhi Chen; Weirong Wang, Shiliang Kang, Wentao Cui, Hang Zhang, Guanliang Yu, Ting Wang, Guoping Dong, Chun Jiang, Shifeng Zhou, Jianrong Qiu
      Abstract: White lasers are promising illuminants for emerging visible light communication, which can overcome bottlenecks of lower energy conversion efficiencies and output powers in traditional white light-emitting (WLE) diodes. However, optical gain materials for white lasers are suffering from great challenges of material growth and growth-compatible cavity structure where lasing of all three elementary colors can be supported simultaneously. Here, an exquisite physical strategy is demonstrated to realize simultaneous red, green, and blue (RGB) upconversion (UC) photoluminescence for white light modulation for the first time, namely using dual lasers at 850 and 980 nm to stimulate easy-fabricated glass ceramics (GCs) fiber laser materials (Pr3+ single-doped germanium oxyfluoride GCs). It is shown that tailorable white light is much more sensitive to lower dopant concentration for GCs than that for glass. Furthermore, compared to glass, UC fluorescence intensities in GCs have approximately two orders of magnitude enhancement. The feasibility of the judicious dual-lasers excitation tactic is validated for high efficacious RGB fluorescence emission for white light from Pr3+ single-doped GCs via electronics transition dynamics and theoretical calculations. The white light emission from Pr3+ single-doped GCs, adjusted by simultaneous dual-lasers excitation, may open a novel door to develop white light GCs fiber lasers for application in future wireless communication.Simultaneous three-fundamental-colors upconversion emission for white light modulation has been demonstrated in Pr3+ single-doped glass ceramics (GCs) via simultaneous dual-wavelength pumping at 850 and 980 nm. Significantly, this facile dual-lasers pumping approach, tailoring white light from Pr3+ single-doped GCs, will prompt the development of white light GCs fiber lasers for application in future Li-Fi communication.
      PubDate: 2017-12-22T07:15:58.858899-05:
      DOI: 10.1002/adom.201700787
  • Broadband Terahertz Circular-Polarization Beam Splitter
    • Authors: Wendy S. L. Lee; Shruti Nirantar, Daniel Headland, Madhu Bhaskaran, Sharath Sriram, Christophe Fumeaux, Withawat Withayachumnankul
      Abstract: Splitting circularly polarized waves is desirable for high-data-rate wireless communications and study of molecular chirality at terahertz frequencies. Typically, this functionality is achieved using bulk optical systems with limitations in material availability, bandwidth, and efficiency. As an alternative, metasurfaces with spatially varying broadband birefringence are employed to attain the same functionality. It is demonstrated that a metasurface designed with gradually rotated birefringent resonators can deflect normally incident left-handed circularly polarized and right-handed circularly polarized waves into different directions. This beam splitting functionality is maintained over an experimentally demonstrated relative deflection bandwidth of 53%, namely, covering the band of 0.58–1.00 THz.The fabricated metasurface consisting of metallic coaxial disk-ring resonators is capable of deflecting normally incident left- and right-handed circularly polarized waves into opposite directions. Furthermore, this beam splitting capability is preserved over a broadband range and is highly efficient. Potential applications include polarization multiplexing in terahertz communications and analyzing the response of chiral molecules.
      PubDate: 2017-12-22T02:01:58.703804-05:
      DOI: 10.1002/adom.201700852
  • Strong Exciton–Photon Coupling in Hybrid Inorganic–Organic
           Perovskite Micro/Nanowires
    • Authors: Shuai Zhang; Qiuyu Shang, Wenna Du, Jia Shi, Zhiyong Wu, Yang Mi, Jie Chen, Fengjing Liu, Yuanzheng Li, Mei Liu, Qing Zhang, Xinfeng Liu
      Abstract: Recently, inorganic–organic perovskite nanowires with strong photon confinement and isotropy have attracted considerable attention for advanced applications in optoelectronic devices from lasers and photodetectors to transistors. Moreover, their high exciton oscillation strength and binding energy make them very promising for polariton devices in the strong light–matter interaction region. This study presents the strong exciton–photon coupling in hybrid inorganic–organic CH3NH3PbBr3 micro/nanowire cavities at room temperature. Clear anticrossing feature is observed by using remote excitation photoluminescence emission spectroscopy with vacuum Rabi splitting energy up to 390 meV. The observed vacuum Rabi splitting energy of up to ≈390 meV (0.32 × 3.66 µm2) is attributed to large oscillator strength and photon confinement in reduced dimension of the micro/nanowire based Fabry–Pérot cavities. With increasing pump fluence, the exciton–photon coupling is weakened because of carrier screening effect, which leads to the occurrence of photonic lasing instead of polariton lasing. The demonstrated strong exciton–photon coupling in perovskite micro/nanowire cavities is significant for the development of high performance polariton-based incoherent and coherent light sources, nonlinear optics, and slow light applications.Strong exciton–photon coupling in hybrid inorganic–organic CH3NH3PbBr3 micro/nanowire cavities at room temperature is presented. By using remote excited emission spectroscopy, anticrossing with vacuum Rabi splitting energy up to ≈390 meV is observed. With increasing pump fluence, the exciton–photon coupling is weakened, which leads to photonic lasing insted of polariton lasing.
      PubDate: 2017-12-21T06:11:59.795755-05:
      DOI: 10.1002/adom.201701032
  • Implantable and Biodegradable Poly(l-lactic acid) Fibers for Optical
           Neural Interfaces
    • Authors: Ruxing Fu; Wenhan Luo, Roya Nazempour, Daxin Tan, He Ding, Kaiyuan Zhang, Lan Yin, Jisong Guan, Xing Sheng
      Abstract: Advanced optical fibers and photonic structures play important roles in neuroscience research, along with recent progresses of genetically encoded optical actuators and indicators. Most techniques for optical neural implants rely on fused silica or long-lasting polymeric fiber structures. In this paper, implantable and biodegradable optical fibers based on poly(l-lactic acid) (PLLA) are presented. PLLA fibers with dimensions similar to standard silica fibers are constructed using a simple thermal drawing process at around 220 °C. The formed PLLA fibers exhibit high mechanical flexibility and optical transparency, and their structural evolution and optical property changes are systematically studied during in vitro degradation. In addition, their biocompatibility with brain tissues is evaluated in living mice, and full in vivo degradation is demonstrated. Finally, PLLA fibers are implemented as a tool for intracranial light delivery and detection, realizing deep brain fluorescence sensing and optogenetic interrogation in vivo. The presented materials and device platform offer paths to fully biocompatible and bioresorbable photonic systems for biomedical uses.Implantable and biodegradable poly(l-lactic acid) fibers are constructed using a simple thermal drawing process at around 220 °C. Their structural evolution and optical property changes are systematically studied during in vitro degradation. The fibers are implemented for deep brain fluorescence sensing and optogenetic interrogation in vivo.
      PubDate: 2017-12-21T06:10:27.102793-05:
      DOI: 10.1002/adom.201700941
  • Pressure-Induced Wide-Range Reversible Emission Shift of
           Triphenylamine-Substituted Anthracene via Hybridized Local and Charge
           Transfer (HLCT) Excited State
    • Authors: Aisen Li; Zhiyong Ma, Jinxia Wu, Ping Li, Hailong Wang, Yijia Geng, Shuping Xu, Bing Yang, Houyu Zhang, Haining Cui, Weiqing Xu
      Abstract: 4-(Anthracen-9-yl)-N,N-diphenylaniline (TPA-AN) is a typical molecule belonging to a donor–acceptor system. Here, the ordered crystal and the powder of TPA-AN are used for high-pressure Raman and fluorescence experiments, and their spectroscopic features under the shearing force of grinding and the hydrostatic pressure applied by a diamond anvil cell (DAC) are compared. The mechanochromism of TPA-AN is discussed in detail based on the analysis of its single-crystal structure and pressure-driven spectral changes. During the DAC compression process, the TPA-AN crystal shows an obvious emission band shift (from 476 to 600 nm) along with a new intramolecular charge transfer state that is separated from the hybridized local and charge transfer excited state and extremely sensitive to external force. Once the pressure is relieved, the Raman and fluorescence spectra both entirely self-recover without a secondary force. To the authors' knowledge, TPA-AN crystal is one of the largest emission shift organic mechanochromic fluorescent materials among reported publications. The reversible mechanochromic property of TPA-AN for a wide-range emission shift implies a great application potential as smart stimuli-responsive layer in the fields of sensing, organic light-emitting diode displays, and data storage.The mechanochromic features of TPA-AN crystal and powder were investigated. The TPA-AN crystal supports a wide-range emission shift under a relatively low pressure by the pressure-enhanced intermolecular interactions and it can self-recover no matter whether under the anisotropic grinding or isotropic compression. Mechanochromism of TPA-AN dominated by HLCT excited state is extremely sensitive to external force.
      PubDate: 2017-12-21T06:06:58.910672-05:
      DOI: 10.1002/adom.201700647
  • Excitonic Creation of Highly Luminescent Defects In Situ in Working
           Organic Light-Emitting Diodes
    • Authors: Yong-Biao Zhao; Grayson L. Ingram, Xi-Wen Gong, Xi-Yan Li, Li-Na Quan, Pei-Cheng Li, Jia-Qi Xie, Edward H. Sargent, Zheng-Hong Lu
      Abstract: Excitons play the central role in organic optoelectronic devices. Efficient exciton-to-photon and photon-to-electron conversion promote quantum yield in optoelectronic devices such as organic light-emitting diodes and organic solar cells. Exciton-related reaction products and defects in working devices have previously been viewed as fatal to stability. Here, the utilization of these excitonic reactions to create luminescent defects with extremely high (6.7%) external quantum efficiency in an operating device containing 1,1-bis((di-4-tolylamino)phenyl) cyclohexane (TAPC) is reported. Transient photoluminescence reveals a long delayed fluorescence lifetime (2.7 µs) from these emissive defects, indicating that they exhibit thermally activated delayed fluorescence. It is shown that the functional group of tri-p-tolylamine (TPTA) follows similar processes as TAPC, suggesting that the chemical nature of the observed luminescent defects is directly related to TPTA.Excitonic processes in working organic light-emitting diodes are engineered to produce extremely highly luminescent thermally activated delayed fluorescence defects with extremely high (>18 cd A−1) current efficiencies.
      PubDate: 2017-12-21T03:06:29.661236-05:
      DOI: 10.1002/adom.201700856
  • Few-Layer Tin Sulfide: A Promising Black-Phosphorus-Analogue 2D Material
           with Exceptionally Large Nonlinear Optical Response, High Stability, and
           Applications in All-Optical Switching and Wavelength Conversion
    • Authors: Leiming Wu; Zhongjian Xie, Lu Lu, Jinlai Zhao, Yunzheng Wang, Xiantao Jiang, Yanqi Ge, Feng Zhang, Shunbin Lu, Zhinan Guo, Jie Liu, Yuanjiang Xiang, Shixiang Xu, Jianqing Li, Dianyuan Fan, Han Zhang
      Abstract: As an analogue compound of black phosphorus, a new 2D semiconducting few-layer SnS is successfully synthesized, and its nonlinear optical response is investigated. It is shown that its nonlinear refractive index and third-order nonlinear susceptibility are measured as n2 ≈ 10−5 (cm2 W−1) and χmonolayer(3) ≈ 10−10 (e.s.u.), respectively. By taking advantage of such a large Kerr nonlinearity, an all-optical switching technique based on few-layer SnS is realized through modulating the propagation of the signal beam by another controlling beam. The achievement of all-optical switching indicates that few-layer SnS could be developed as an excellent optical material for all-optical signal processing. More importantly, a conceptually new and reliable information conversion system based on spatial cross-phase modulation in few-layer SnS, that is, the transmission and conversion of a sequence of bit information from one wavelength channel to the other, is presented. The contributions reveal potential applications of few-layer SnS as a new type of optical information material, and it is therefore anticipated that SnS and other IV–VI compound-based 2D nanomaterials could find promising applications in photonic devices such as optical modulators, optical switches, detectors, etc.By taking advantage of the Kerr nonlinearity, an all-optical switching technique based on few-layer SnS is realized through modulating the propagation of the signal beam by another controlling beam. The achievement of all-optical switching indicates that few-layer SnS could be developed as an excellent optical material for all-optical signal processing.
      PubDate: 2017-12-19T07:00:59.22751-05:0
      DOI: 10.1002/adom.201700985
  • Revisiting the Optical Band Gap in Epitaxial BiFeO3 Thin Films
    • Authors: Daniel Sando; Cécile Carrétéro, Mathieu N. Grisolia, Agnès Barthélémy, Valanoor Nagarajan, Manuel Bibes
      Abstract: A detailed structural and optical band gap characterization study for more than 40 epitaxial bismuth ferrite (BiFeO3—BFO) thin films, measured by X-ray diffraction, atomic force microscopy, and optical transmission spectroscopy, is reported. The films are grown in different deposition systems to varying thicknesses (10–140 nm), on several substrates, and under different growth and cooling conditions. Using the results and literature data, first it is shown that the band gap measured by transmission is systematically lower than the gap found by ellipsometry, suggesting that sufficient caution must be exercised when comparing optical properties of BFO thin films. Then, statistical analysis is used to look for correlations between the band gap and structural parameters. While earlier works show the band gap to be sensitive to epitaxial (homogeneous) strain, it is found that it appears not to exhibit a dependence on inhomogeneous strain, out-of-plane lattice constant, or substrate/film interface roughness. Rather, it is found that surface roughness as well as film thickness generally tends to enhance the gap. Overall, the insensitivity of the band gap to structural parameters—aside from homogeneous strain—makes BiFeO3 largely immune to deviations in processing parameters, which should be an asset for photonic devices based on this material.Using transmission measurements on a large ensemble of epitaxial films, the authors show that the optical band gap of epitaxial BiFeO3 films is largely insensitive to a wide range of processing parameters, including growth temperature, oxygen pressure, and strain gradients in the films.
      PubDate: 2017-12-19T02:06:07.767052-05:
      DOI: 10.1002/adom.201700836
  • Polyphenylnaphthalene as a Novel Building Block for High-Performance
           Deep-Blue Organic Light-Emitting Devices
    • Authors: Wen-Cheng Chen; Yi Yuan, Ze-Lin Zhu, Zuo-Quan Jiang, Liang-Sheng Liao, Chun-Sing Lee
      Abstract: A new member of polycyclic aromatic hydrocarbons named 1,2,3,4-tetraphenylnaphthalene (TNa) is exploited and used as a potential building block in deep-blue organic light-emitting devices (OLEDs) for the first time. By incorporating TNa with phenanthroimidazole, three blue emitters named TNa-PI, TNa-BPI, and TNa-DPI featuring different length of phenyl linkers are designed and synthesized via a facile approach, and systematically characterized with thermal, morphological, theoretical, photophysical, electrical, and electroluminescent (EL) studies. The new fluorophores show intramolecular charge transfer properties in excited state evidenced by positive solvatochromic effect in emission. Theoretical calculation suggests that TNa serves as an electron acceptor in the new molecules. All the new materials can emit intense deep-blue fluorescence in thin film and show bipolar carrier transport properties, with electron conductivity much better than that of hole. Nondoped OLEDs based on TNa-DPI exhibit excellent EL performance with a maximum external quantum efficiency (EQE) of 5.78% and deep-blue emission with color purity of (0.152, 0.085). Furthermore, in the 30 wt.% doped device, TNa-PI emits efficient violet-blue EL with Commission Internationale de l'Èclarage coordinates of (0.156, 0.043) and shows a decent EQE of 2.52% at a practical brightness of 1000 cd m−2.A “piece of graphene” 1,2,3,4-tetraphenylnaphthalene (TNa) is exploited as a novel building block for efficient deep-blue organic light-emitting devices. The as-designed TNa materials can emit intense deep-blue photoluminescence and show high electron transport properties. High device performances (external quantum efficiency> 5%) and deep-blue (Commission Internationale de l'Èclarage, CIEy ≤ 0.08) electroluminescence can be simultaneously achieved by using the new TNa derivatives as emitters.
      PubDate: 2017-12-19T02:00:59.564784-05:
      DOI: 10.1002/adom.201700855
  • Continuous-Wave Lasing in Cesium Lead Bromide Perovskite Nanowires
    • Authors: Tyler J. S. Evans; Andrew Schlaus, Yongping Fu, Xinjue Zhong, Timothy L. Atallah, Michael S. Spencer, Louis E. Brus, Song Jin, X.-Y. Zhu
      Abstract: Lead halide perovskite nanowires (NWs) have been demonstrated in pulsed lasing with high quantum yields, low thresholds, and broad tunability. However, continuous-wave (CW) lasing, necessary for many optoelectronic applications, has not been achieved to date. This is thought to be due to many-body screening, which reduces the excitonic resonance enhancement of the oscillator strength at high excitation densities necessary for population inversion. Here CW lasing in CsPbBr3 perovskite NWs is reported. Analysis of the cavity modes and their temperature dependence reveals that both CW and pulsed lasing originate from polariton modes near the bottleneck region on the lower polariton branch, with a vacuum Rabi splitting of 0.20 ± 0.03 eV. These findings suggest that lead halide perovskite NWs may serve as low-power CW coherent light sources and as model systems for polaritonics in the strong-coupling regime.Optically pumped, continuous-wave lasing in a CsPbBr3 nanowire is enabled by strong confinement-enhanced light–matter coupling. Nanowire waveguide-cavity photons are strongly coupled to the CsPbBr3 exciton resonance to give suboptical bandgap exciton–polariton states that undergo stimulated emission. The Rabi splitting is quantified by modeling the light leaking out at the end facets. This interaction leads to low-threshold lasing and high effective Q-factors.
      PubDate: 2017-12-18T05:59:21.774151-05:
      DOI: 10.1002/adom.201700982
  • Electrically Switchable, Hyper-Reflective Blue Phase Liquid Crystals Films
    • Authors: Xiaowan Xu; Zhen Liu, Yanjun Liu, Xinhai Zhang, Zhigang Zheng, Dan Luo, Xiaowei Sun
      Abstract: Blue phase liquid crystals (BPLCs) with three-dimensional periodicity have attracted significant attention due to their fast response time in the submillisecond region, which is critical in sequential liquid crystal displays and fast switchable photonic devices. However, the reflectivity of single-layer BPLC films in the visible range, which is generally used for reflective display, is still low and limited to 50%, which hinders its use in a wide range of applications. Herein, hyper-reflective, electrically switchable, fast responsive, and colorful reflective displays are demonstrated, which are based on multi-layer BPLC films consisting of two single-layer BPLC templates with opposite handedness. Hyper-reflectivities of 89%, 82%, and 68% in the red, green, and blue color regions are achieved by refilling multi-layer BPLC templates with achiral nematic liquid crystals. A reflectance switching of the film is achieved by unwinding the helical structure of the blue phase in an electric field, where the highest reflectance achieved in the red, green, and blue color regions is 94%, 86%, and 72%, respectively, in the presence of an electric field of 1 V µm−1. Compared to previously demonstrated BPLC films, this newly developed multi-layer BPLC film substantially improves the overall reflection efficiency by up to 3.6 times. Our study on hyper-reflective BPLC film provides an attractive platform for future development including sequential colorful reflective displays and switchable optoelectronic devices.Blue phase superstructure films with hyper-reflectance in red, green, and blue are achieved, which provide an attractive platform for the future development of advanced displays, photonic and soft matter devices.
      PubDate: 2017-12-18T04:17:55.578627-05:
      DOI: 10.1002/adom.201700891
  • Rare Earth Ion-Doped CsPbBr3 Nanocrystals
    • Authors: Qingsong Hu; Zha Li, Zhifang Tan, Huaibing Song, Cong Ge, Guangda Niu, Jiantao Han, Jiang Tang
      Abstract: Rare earth ions Eu3+ and Tb3+ are doped into CsPbBr3 nanocrystals (NCs) for the first time, utilizing a one-pot ultrasonication method. As-synthesized NCs exhibit dual emissions from NCs and rare earth ions, further strengthening the competitiveness of perovskite NCs for lighting application.CsPbBr3 nanocrystals doped with rare earth ions Eu3+ and Tb3+ are fabricated through one-pot ultrasonication. The as-synthesized nanocrystals exhibit similar perovskite phase as undoped CsPbBr3. Multiple color emission is achieved through controlled doping.
      PubDate: 2017-12-18T04:15:50.208329-05:
      DOI: 10.1002/adom.201700864
  • Boosting the Photoluminescence of Monolayer MoS2 on High-Density Nanodimer
           Arrays with Sub-10 nm Gap
    • Authors: Qi Hao; Jinbo Pang, Yang Zhang, Jiawei Wang, Libo Ma, Oliver G. Schmidt
      Abstract: Patterned plasmonic nanodimers are fabricated exploiting an ultrathin porous anodic aluminum oxide membrane as a mask during angle-resolved shadow deposition. The fabricated nanodimer arrays exhibit consistent sub-10 nm gaps and a high particle density up to 1.0 × 1010 cm−2 over a large area. The ultrasmall dimer gaps provide highly confined electromagnetic fields, which strongly enhance the photoluminescence (PL) emission and Raman scattering from the surrounding monolayer molybdenum disulphide (MoS2). The ensemble PL intensity from MoS2/dimers is enhanced by up to a factor of ≈160 by resonant excitation of the dimer modes. Anisotropic polarization-dependent characteristics of PL and Raman from the MoS2/dimers confirm that the dominant enhancement originates from the dimer configuration. These experiments demonstrate a facile approach for the fabrication of low-cost high-performance 2D material-based optoelectronic devices.Patterned dimers with consistent sub-10 nm gaps and a high particle density up to 1.0 × 1010 cm−2 are fabricated by utilizing an ultrathin anodic aluminum oxide membrane. The ensemble photoluminescence emission from molybdenum disulphide (MoS2) is enhanced by 160-fold due to strongly confined electromagnetic fields from the dimers, and polarization-dependent characteristics from MoS2/dimers are revealed.
      PubDate: 2017-12-18T03:49:47.910306-05:
      DOI: 10.1002/adom.201700984
  • Lithography-Free, Omnidirectional, CMOS-Compatible AlCu Alloys for
           Thin-Film Superabsorbers
    • Authors: Mariama Rebello Sousa Dias; Chen Gong, Zackery A. Benson, Marina S. Leite
      Abstract: Superabsorbers based on metasurfaces have recently enabled the control of light at the nanoscale in unprecedented ways. Nevertheless, the sub-wavelength features needed to modify the absorption band usually require complex fabrication methods, such as electron-beam lithography. To overcome the scalability limitations associated with the fabrication of metallic nanostructures, engineering the optical response of superabsorbers by metal alloying is proposed, instead of tuning the geometry/size of the nanoscale building blocks. The superior performance of thin film AlCu alloys as the metallic component of planar bilayer superabsorbers is numerically demonstrated. This alloy outperforms its pure constituents as well as other metals, such as Ag, Au, and Cr. As a model system, a Si/AlCu structure is analyzed that presents>99% absorption at selected wavelength ranging from the visible to the near-infrared regions of the spectrum, depending on the subwavelength thickness of the semiconductor. The multi-wavelength near-unity absorption behavior of Si/AlCu persists even for oblique angle of incidence, up to 70°. Additionally, the findings are validated by fabricating and testing a-Si/AlCu superabsorbers, where good agreement is found between the numerically and experimentally determined optical response. The system investigated here is relevant for integration in complementary metal-oxide-semiconductor (CMOS) technologies.Complementary metal–oxide–semiconductor-compatible metal alloys formed by earth-abundant materials enable near-unity absorption (>99%) on the vis-NIR. It is demonstrated that Si/AlCu produce multi-wavelength, omnidirectional superabsorption in a thin-film configuration, outperforming its pure metal constituents and other metals such as Ag and Au. Metallic alloys can be effectively implemented as active elements in photonic devices.
      PubDate: 2017-12-13T05:26:32.778942-05:
      DOI: 10.1002/adom.201700830
  • Efficient Optical-to-THz Conversion Organic Crystals with Simultaneous
           Electron Withdrawing and Donating Halogen Substituents
    • Authors: Seung-Jun Lee; Bong Joo Kang, Myeong-Hoon Shin, Seung-Chul Lee, Seung-Heon Lee, Mojca Jazbinsek, Hoseop Yun, Dongwook Kim, Fabian Rotermund, O-Pil Kwon
      Abstract: This study reports on highly efficient nonlinear optical ionic quinolinium crystals with various aromatic anions possessing different spatial volume for controlling the space-filling characteristics and introducing halogen substituents having simultaneous electron-withdrawing and electron-donating effects. The quinolinium crystals with chloro and bromo substituents having simultaneous electron-withdrawing and electron-donating effects on anions exhibit perfect molecular ordering for optimizing the diagonal second-order nonlinear optical response, while the fluoro substituent having relatively small electron-donating effects on anions results in the absence of nonlinear optical response. Compared to widely used 4-methylbenzenesulfonate, the chloro substituent on 4-chlorobenzenesulfonate (CBS) results in decreasing π–π interactions between cations and anions. This leads on the one hand to an enhanced macroscopic nonlinear response and on the other hand to an increased strength of hydrogen bonds between anions, resulting in strong suppression of THz phonon vibration. In THz generation measurements with pump pulses at 1300 nm, 0.39 mm thick 2-(4-hydroxystyryl)-1-methylquinolinium 4-chlorobenzenesulfonate (OHQ-CBS) crystal exhibits excellent optical-to-THz conversion characteristics with 27 times higher peak-to-peak electric field and 3 times broader bandwidth than the well-known 1.0 mm thick inorganic standard ZnTe crystal. In addition, compared to state-of-the-art analogous quinolinium crystals with 4-methylbenzenesulfonate, OHQ-CBS crystal exhibits 1.8 times higher field.For the molecular design of ionic organic nonlinear optical crystals, controlling space-filling characteristics by introducing substituents with simultaneous electron-withdrawing inductive and electron-donating resonance effects is promising for enhancing the macroscopic optical nonlinearity and suppressing phonon vibrations for efficient THz wave generation.
      PubDate: 2017-12-13T02:55:57.859772-05:
      DOI: 10.1002/adom.201700930
  • Electroluminescence of Colloidal Quantum Dots in Electrical Contact with
           Metallic Nanoparticles
    • Authors: Hongyue Wang; Quynh Le-Van, Abdelhanin Aassime, Xavier Le Roux, Fabrice Charra, Nicolas Chauvin, Aloyse Degiron
      Abstract: The electroluminescence of a carpet of colloidal quantum dots in electrical contact with a metal nanoparticle array is investigated. The properties of the structures spectacularly differ from the well-known behavior of point sources placed at nonvanishing distances from subwavelength scatterers (robustness to quenching, coupling primarily defined by the electrical contact between the two species, etc.). This regime of short-range interactions can even be enabled with nonplasmonic inclusions made of platinum, providing an extreme case of enhanced and tailored light emission by quantum emitters in a highly absorptive environment. As a corollary, surface plasmons are not a necessary or sufficient ingredient but add functionalities that nonplasmonic structures do not possess. These findings indicate that the physics of localized light emitters in highly inhomogeneous environments is far from being fully understood and have important implications for the next generation of active metamaterials and advanced optoelectronic devices.The electroluminescence of colloidal quantum dots exhibits unexpected and technology-enabling properties when the emitters are brought in electrical contact with metallic nanoparticles. The hybridization between the two species is robust to quenching, goes beyond plasmonics, and opens up new paths for active metamaterials and other advanced optoelectronic devices.
      PubDate: 2017-12-04T08:25:40.847933-05:
      DOI: 10.1002/adom.201700658
  • Terahertz Modulators Based on Silicon Nanotip Array
    • Authors: Zhong-Wei Shi; Xing-Xing Cao, Qi-Ye Wen, Tian-Long Wen, Qing-Hui Yang, Zhi Chen, Wen-Sheng Shi, Huai-Wu Zhang
      Abstract: As an attractive applications of terahertz (THz) radiation, imaging with THz technique stands at the focus of current interest. THz spatial modulators are key issue for fast imaging with a single detector. Here, for the first time, the silicon nanotip (SiNT) arrays are reported that can be utilized as antireflection layers for the THz wave to achieve a low-loss and spectrally broadband optical-driven THz modulator. Compared with the modulator fabricated with bare silicon, a 2–3-time larger modulation depth is achieved in SiNT modulator. Moreover, it is found that the intrinsic THz transmission of SiNT is as high as 90%, which is much higher than that of bare silicon. The theoretical simulation results reveal that a strong antireflection effect induced from SiNT layer plays a crucial role in enhancing the properties of modulator. The SiNT-based optical-driven THz modulator with low loss and high modulation depth is promising for potential application to THz imaging.New applications in the realms of terahertz (THz) technology require versatile adaptive optics and powerful modulation techniques. Semiconductors have proven to provide fast and broadband all-optical THz wave modulation. In this work, the silicon nanotip arrays on silicon substrate are utilized as antireflection layers for the THz wave, achieving a low-loss and spectrally broadband optical-driven THz modulator with remarkably enhanced modulation depth.
      PubDate: 2017-12-04T02:37:02.518022-05:
      DOI: 10.1002/adom.201700620
  • Printing of Large-Scale, Flexible, Long-Term Stable Dielectric Mirrors
           with Suppressed Side Interferences
    • Authors: Carina Bronnbauer; Arne Riecke, Marius Adler, Julian Hornich, Gerhard Schunk, Christoph J. Brabec, Karen Forberich
      Abstract: Dielectric mirrors are wavelength-selective mirrors which are based on thin film interference effects. Their optical band can precisely be adjusted in width, position, and reflectance by the refractive index of the applied materials, the layers' thicknesses, and the amount of deposited layers. Nowadays, they are a well-known light management tool for efficiency enhancement in, for example, semitransparent organic solar cells (OSCs) and light guiding in organic light-emitting diodes (OLEDs). However, most of the dielectric mirrors are still fabricated by lab-scale techniques such as spin-coating or physical vapor deposition under vacuum. Large-scale, fully printed (maximum 20 × 20 cm2) dielectric mirrors with adjustable reflectance characteristics are fabricated, using temperatures of maximum 50 °C and alcohol-based inks. According to the moderate processing conditions they can be easily deposited not only on rigid glass substrates but also on flexible foils. They show high stability against humidity, light irradiation, and temperature, positioning themselves as good candidates for applications in OLEDs and OSCs. Eventually, by simulations and experiments it is verified that a moderate degree of variations in layer thickness and surface roughness can suppress side interference fringes, while not impacting the main transmittance minimum or the main reflection maximum, respectively.Dielectric mirrors with high optical quality and easily adjustable spectral characteristics are printed on large-area glass and plastic substrates. Furthermore, the mirrors exhibit high stability under humidity, heat, and light exposure. Using optical simulations, it is concluded that the transmittance in the short-wavelength region is related to the roughness of the interfaces between the separate layers.
      PubDate: 2017-12-04T02:36:39.946651-05:
      DOI: 10.1002/adom.201700518
  • Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser
    • Authors: Owies M. Wani; Hao Zeng, Piotr Wasylczyk, Arri Priimagi
      Abstract: A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light-induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light-responsive octopod, are demonstrated. The reported technique enables easy and cost-effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.Programmed photoresponses are inscribed into monolithic actuators made of liquid crystal polymer networks, using a laser projector and photoalignment technique. Distinct light-induced shape changes, such as bending, buckling, coiling, gripping, and octopus-like motion, driven by both photochemical and photothermal actuation are demonstrated. The reported technique enables easy and efficient programming in actuation, thereby significantly facilitating the realization of functional soft robots.
      PubDate: 2017-12-04T02:36:11.989514-05:
      DOI: 10.1002/adom.201700949
  • All-Inorganic Perovskite Quantum Dots/p-Si Heterojunction Light-Emitting
           Diodes under DC and AC Driving Modes
    • Authors: Jingjing Liu; Xuexi Sheng, Yangqing Wu, Dongke Li, Jianchun Bao, Yang Ji, Zewen Lin, Xiangxing Xu, Linwei Yu, Jun Xu, Kunji Chen
      Abstract: Light-emitting diodes based on perovskite quantum dots have attracted much attention since they can be applied in low-cost display, biosensors, and other optoelectronic devices. Here, all-inorganic light-emitting diodes based on n-type perovskite quantum dots/p-Si heterojunction are fabricated. Both the green and the red light emission are achieved at room temperature. The output power density is 0.14 mW cm−2 for green light device and 0.25 mW cm−2 for the red one. The relatively low turn on voltage and high emission intensity in red light device can be attributed to the small hole injection barrier between CsPbI3 quantum dots and p-Si. The emission drop off at high current density is observed under direct current (DC) driving mode, which is significantly improved by applying alternating current (AC) square pulses. The enhanced electroluminescence and the improved operation stability at high current density under AC driving mode can be attributed to the less thermal degradation and the reduced charge accumulation in the interface defect states due to the alternated biases. The results demonstrate the possibility of integrating the perovskite quantum dots with Si platform, which will be helpful to extend their actual applications.All-inorganic light-emitting diodes based on n-type perovskite quantum dots/p-Si heterojunction are fabricated. Both the green and the red light emission are achieved at room temperature. The enhanced electroluminescence and improved operation stability under alternating current driving mode can be attributed to the less thermal degradation and the reduced charge accumulation in the interface defects states due to the alternated biases.
      PubDate: 2017-12-04T02:35:48.180785-05:
      DOI: 10.1002/adom.201700897
  • WO3-Based Electrochromic Distributed Bragg Reflector: Toward Electrically
           Tunable Microcavity Luminescent Device
    • Authors: Lili Xiao; Ying Lv, Jie Lin, Yongsheng Hu, Wenjie Dong, Xiaoyang Guo, Yi Fan, Nan Zhang, Jialong Zhao, Yunjun Wang, Xingyuan Liu
      Abstract: The electroresponsive WO3-based electrochromic distributed Bragg reflectors (ECDBRs) are fabricated by means of one-step, room temperature glancing-angle electron-beam evaporation. The reflectance and Bragg wavelength of ECDBRs can be precisely and reversibly tailored on a large scale by simply applying a small bias voltage (±1.1 V) due to the electrochromic effect of the WO3 layer, and this unique character is utilized to construct an electrically tunable microcavity luminescent device with embedded green CdSe@ZnS quantum dots (QDs). Therefore, large and reversible modulation in terms of photoluminescence (PL) peak intensity (18–335%), PL peak position (from 510.3 to 525.8 nm), and full width at half maximum (from 21.8 to 11.4 nm) from QDs in microcavity are achieved under electrical stimulus. The results will potentially provide a straightforward voltage-control route toward broadband tunable microcavity electroluminescent and lasing devices.The electrochromic distributed Bragg reflector based on monomaterial of WO3 with different porosity is successfully fabricated and used to construct an electrically tunable microcavity luminescent device, which shows large and reversible changes in photoluminescence and provides an instructive guidance toward electroactive optical and optoelectronic devices.
      PubDate: 2017-12-01T03:11:49.38782-05:0
      DOI: 10.1002/adom.201700791
  • Generation of Radial Polarized Lorentz Beam with Single Layer Metasurface
    • Authors: Jin-Ying Guo; Xin-Ke Wang, Jing-Wen He, Huan Zhao, Sheng-Fei Feng, Peng Han, Jia-Sheng Ye, Wen-Feng Sun, Guo-Hai Situ, Yan Zhang
      Abstract: A radially polarized Lorentz beam is demonstrated in the terahertz waveband with a single layer metasurface. Composed of cross antennas of various sizes and orientation, the metasurface performs simultaneously a continuous amplitude modulation and a controlled polarization spatial redistribution of incident waves of wavelength 400 µm. The metasurface device is designed and characterized using a terahertz time domain spectral imaging system. Experimental results are consistent with theoretical calculations. With the advantage of compactness and simplicity, this device may be applied to generate various complex light fields and in the reconstruction of computer-generated polarization hologram.Consecutive redistribution of polarization and transmittance is simultaneously achieved with a single layer metasurface. A sample is designed to generate a radial polarized Lorentz beam in the THz region, and the experimental results fit with simulation well. This kind of device can be used in the reconstruction of complex light field and computer generated polarization hologram.
      PubDate: 2017-12-01T03:10:55.655375-05:
      DOI: 10.1002/adom.201700925
  • High and Fast Response of a Graphene–Silicon Photodetector Coupled with
           2D Fractal Platinum Nanoparticles
    • Authors: Kun Huang; Yucong Yan, Ke Li, Afzal Khan, Hui Zhang, Xiaodong Pi, Xuegong Yu, Deren Yang
      Abstract: 2D material-based electronic devices like graphene–silicon photodetectors (Gr–Si PDs) have attracted much attention of researchers in the past few years. Due to the nature of Schottky junction, Gr–Si PDs have ultrafast response. However, responsivity of Gr–Si PDs is very low, which hinders their practical application. Low work function of Gr and poor absorbance of Si are mainly responsible for this problem. Here, a novel approach for coupling of Gr–Si PDs with 2D fractal platinum nanoparticles (Pt NPs) is demonstrated to enhance the responsivity and speed up the response of Gr–Si PDs at the same time. 2D morphology of fractal Pt NPs helps to overcome the coffee-ring effect. Fully covered fractal Pt NPs remarkably improve the absorption of Gr–Si PDs by plasmonic effect. Responsivity of Gr–Si PDs thus is remarkably enhanced to 26 A W−1. Meanwhile, work function of Gr is improved by the physical doping of high-work-function Pt NPs. Therefore, the Schottky barrier of Gr–Si junction is increased, resulting in faster response. Improvement in the built-in electric field reduces the background noise of Gr–Si PDs as well. These results indicate toward a simple and novel approach for fabricating high and fast response Gr–Si PDs.A novel approach to enhance the responsivity and the response speed of graphene–silicon photodetectors is demonstrated with 2D fractal platinum nanoparticles. Fully covered platinum nanoparticles improve the responsivity of photodetectors to 26 A W−1, which outperforms similar photodetectors reported so far.
      PubDate: 2017-12-01T03:10:40.60803-05:0
      DOI: 10.1002/adom.201700793
  • Toward High Uniformity of Photoresponse Broadband Hybrid
           Organic–Inorganic Photodiode Based on PVP-Modified Perovskite
    • Authors: Feiyu Zhao; Kun Xu, Xiao Luo, Yuanlong Liang, Yingquan Peng, Feiping Lu
      Abstract: Broadband photodiode based on Si/perovskite structure that combines the advantages of both silicon and perovskite is presented in this paper. This study addresses the issue of the absent of ultraviolet absorption of silicon and the near-infrared absorption of perovskite. More significantly, the polyvinyl pyrrolidone (PVP) modification process on the perovskite film shows efficiency on morphology and crystallizing control that are important for high uniformity of responsivity and reproducibility. The result shows high spectral uniformity of responsivity (uSR = 0.85) on a wide spectrum ranging from 405 to 808 nm and the average of deviation of reproducibility is only 2.1%. Fast response time (645 µs), good on–off switching performance, and high photosensitivity (Ion/Ioff = 1322) of the as-fabricated device are also achieved in this work. This research indicates that the high-performance broadband photodiode can be realized by the novel organic–inorganic structure and PVP modification without compromising any of its performance.Hybrid organic–inorganic photodiodes based on Si/perovskite structure and further modified with polyvinyl pyrrolidone additive are fabricated, realizing high-performance broadband photoresponse from NUV–NIR region. This study explores a new way for broadband photodetector and an efficient process of perovskite film modification.
      PubDate: 2017-11-30T09:22:16.396593-05:
      DOI: 10.1002/adom.201700509
  • Tin-Based Perovskite with Improved Coverage and Crystallinity through
           Tin-Fluoride-Assisted Heterogeneous Nucleation
    • Authors: Min Xiao; Shuai Gu, Pengchen Zhu, Mingyao Tang, Weidong Zhu, Renxing Lin, Chuanlu Chen, Weichao Xu, Tao Yu, Jia Zhu
      Abstract: Tin fluoride (SnF2) is widely used as an effective additive for lead-free tin-based perovskite solar cells. However, the function of SnF2 and the mechanism in improving the film morphology are still not clear. In this work, it is clearly demonstrated that SnF2 can play a crucial role in the crystal nucleation process. Due to the limited solubility, SnF2 creates more nucleuses for the crystal growth and therefore enables more uniform thin film with high coverage. It is confirmed that this mechanism can be applied to the growth of both thin film and single crystal. As a result of tin-fluoride-assisted heterogeneous nucleation, an MASnIBr2-based perovskite solar cell with a high and stable power conversion efficiency of 3.70% is demonstrated.SnF2 can serve as heterogeneous nucleation sites to facilitate crystal growth of tin-based perovskite crystal. The addition of SnF2 with appropriate concentration can enable tin-based perovskite film with full coverage and improved crystallinity and reduced carrier recombination. As a result, a tin-based PSC with stable efficiency of 3.70% is demonstrated.
      PubDate: 2017-11-30T09:21:29.858702-05:
      DOI: 10.1002/adom.201700615
  • High-Efficiency Dielectric Metasurfaces for Polarization-Dependent
           Terahertz Wavefront Manipulation
    • Authors: Huifang Zhang; Xueqian Zhang, Quan Xu, Chunxiu Tian, Qiu Wang, Yuehong Xu, Yanfeng Li, Jianqiang Gu, Zhen Tian, Chunmei Ouyang, Xixiang Zhang, Cong Hu, Jiaguang Han, Weili Zhang
      Abstract: Recently, metasurfaces made up of dielectric structures have drawn enormous attentions in the optical and infrared regimes due to their high efficiency and designing freedom in manipulating light propagation. Such advantages can also be introduced to terahertz frequencies where efficient functional devices are still lacking. Here, polarization-dependent all-silicon terahertz dielectric metasurfaces are proposed and experimentally demonstrated. The metasurfaces are composed of anisotropic rectangular-shaped silicon pillars on silicon substrate. Each metasurface holds dual different functions depending on the incident polarizations. Furthermore, to suppress the reflection loss and multireflection effect in practical applications, a high-performance polarization-independent antireflection silicon pillar array is also proposed, which can be patterned at the other side of the silicon substrate. Such all-silicon dielectric metasurfaces are easy to fabricate and can be very promising in developing next-generation efficient, compact, and low-cost terahertz functional devices.Polarization-dependent all-silicon dielectric metasurfaces are demonstrated for efficiently manipulating the terahertz wavefront. The proposed metasurfaces consist of rectangular silicon pillars, and each functions as two different devices with respect to the x- and y-polarizations. The efficiency of the structural interface can reach about 65%. Besides, a polarization-independent antireflection layer is proposed and characterized, which can greatly reduce the reflection loss.
      PubDate: 2017-11-30T09:20:56.221505-05:
      DOI: 10.1002/adom.201700773
  • Direct Investigation of the Birefringent Optical Properties of Black
           Phosphorus with Picosecond Interferometry
    • Authors: Wei Zheng; Andrei Nemilentsau, Dustin Lattery, Peipei Wang, Tony Low, Jie Zhu, Xiaojia Wang
      Abstract: Black phosphorus (BP) is an emerging 2D semiconducting material with great potential for nanoelectronic and nanophotonic applications, especially owing to its unique anisotropic electrical and optical properties. Many theoretical studies have predicted the anisotropic optical properties of BP, but the direct experimental quantification remains challenging. The difficulties stem from the ease of BP's degradation when exposed to air in ambient conditions, and from the indirect nature of conventional approaches that are subject to large measurement uncertainties. This work reports a direct investigation of the birefringent optical constants of micrometer-thick BP samples with picosecond (ps) interferometry, over the wavelength range from 780 to 890 nm. In this ps-interferometry approach, an ultrathin (5 nm) platinum layer for launching acoustic waves naturally protects the BP flake from degradation. The birefringent optical constants of BP for light polarization along the two primary crystalline orientations, zigzag and armchair, are directly obtained via fitting the attenuated Brillouin scattering signals. A biexponential model is further proposed to analyze the Brillouin scattering signals for a random incident light polarization. The BP experimental results and the associated measurement sensitivity analysis demonstrate the reliability and accuracy of the ps-interferometry approach for capturing the polarization-dependent optical properties of birefringent materials.Black phosphorus (BP) is an emerging 2D semiconducting material with unique anisotropic optical properties. This work reports a direct investigation of the birefringent optical constants of BP with picosecond-interferometry in the near-infrared regime. The birefringent optical constants of BP for light polarization along zigzag and armchair directions are obtained via analyzing the attenuated Brillouin scattering signals.
      PubDate: 2017-11-29T03:20:48.662965-05:
      DOI: 10.1002/adom.201700831
  • Through the Spherical Looking-Glass: Asymmetry Enables Multicolored
           Internal Reflection in Cholesteric Liquid Crystal Shells
    • Authors: Yong Geng; Ju-Hyun Jang, Kyung-Gyu Noh, JungHyun Noh, Jan P. F. Lagerwall, Soo-Young Park
      Abstract: Spheres of cholesteric liquid crystal generate dynamic patterns due to selective reflection from a helical structure subject to continuously curved boundaries. So far the patterns are investigated exclusively as function of reflections at the sphere exterior. Here it is shown that the cholesteric shells in a microfluidics produced double emulsion enable also a sequence of internal reflections if the shells have sufficiently thin top and thick bottom. While such asymmetry is promoted by buoyancy when the internal droplet has lower density than the liquid crystal, the elasticity of the cholesteric helix prefers a symmetric shell geometry, acting against gravity. This subtle balance can hide the internal reflections for long time. Eventually, however, the asymmetry is established, revealing a new class of photonic patterns characterized by colored sharp concentric rings. With the complete knowledge of the diverse light-reflecting behavior of cholesteric liquid crystal shells, and utilizing the tunability of the structure period by, e.g., temperature, electric field, or exposure to various chemical species as well as polymer stabilization for making the shells long-term stable, they may be developed into remarkable new optical elements for photonics, sensing, or security pattern generation.Shells of cholesteric liquid crystal can exhibit colorful rings from internal selective reflection. The shell must be thinner at the top than at the bottom, as promoted by buoyancy if the internal liquid has lower density than the liquid crystal. However, such asymmetry is counteracted by the elasticity of the helix, which favors uniform shell thickness.
      PubDate: 2017-11-20T01:52:26.87816-05:0
      DOI: 10.1002/adom.201700923
  • Strong Coupling in a Photonic Molecule Formed by Trapping a Microsphere in
           a Microtube Cavity
    • Authors: Jiawei Wang; Yin Yin, Qi Hao, Yang Zhang, Libo Ma, Oliver G. Schmidt
      Abstract: A photonic molecule formed by trapping a microsphere cavity into a hollow microtube cavity is demonstrated, which provides a novel design over conventional photonic molecules comprised of solid-core whispering gallery mode microcavities with externally tangent configuration. Periodic spectral modulations of mode intensity, resonant mode shift, and quality factor are observed owing to the largely mismatched cavity sizes. The intercavity coupling strength can be tuned by shifting the excitation position off the tangent point of the microsphere-tube system along the tube axis, rather than the conventional strategy of changing the spacing between coupled cavities. In particular, anticrossing feature of coupled modes is revealed to verify the existence of optical strong coupling in the microsphere-tube system. Numerical simulation results show an excellent agreement with the experimental observations. The present work provides a flexible strategy for designing photonic molecules and tuning the coupling behavior of resonant modes, which is of high interest for both fundamental and applied studies.A photonic molecule formed by trapping a microsphere into a hollow-core microtube cavity is demonstrated. Whispering gallery mode coupling between two size-mismatched cavities leads to a periodical spectral modulation. The coupling strength can be readily tuned by shifting the excitation position along the tube axial dimension. Mode splitting and anti­crossing feature are observed for inter­actions in the strong coupling regime.
      PubDate: 2017-11-20T01:51:44.028612-05:
      DOI: 10.1002/adom.201700842
  • Amplitude Modulation of Anomalously Refracted Terahertz Waves with
           Gated-Graphene Metasurfaces
    • Authors: Teun-Teun Kim; Hyunjun Kim, Mitchell Kenney, Hyun Sung Park, Hyeon-Don Kim, Bumki Min, Shuang Zhang
      Abstract: Although recent progress in metasurfaces has shown great promise for applications, optical properties in metasurfaces are typically fixed by their structural geometry and dimensions. Here, an electrically controllable amplitude of anomalously-refracted waves in a hybrid graphene/metasurface system are experimentally demonstrated, which consists of an artificially constructed two-dimensional metallic apertures array and naturally occurring two-dimensional carbon atoms (graphene) in the subwavelength-scale (< λ/10). Based on Pancharatnam–Berry phase and by careful design of a spatially linear phase profile, it is shown that the amplitude of anomalously refracted circularly cross-polarized terahertz waves can be effectively modulated by an applied gate voltage. The developed electrically tunable graphene metasurfaces may lead to various advanced applications that require dynamical control over electromagnetic waves, such as amplitude tunable active focusing lenses, vortex phase plates and dynamic holography.Electric control of anomalously-refracted waves is demonstrated in a hybrid graphene/metasurface system. Combining two-dimensional apertures based on a concept of Pancharatnam–Berry phase and single-layer graphene, it is shown that the amplitude of anomalously refracted circularly cross-polarized waves can be effectively modulated to a low gate-voltage (< 2.2 V).
      PubDate: 2017-11-20T01:51:16.109801-05:
      DOI: 10.1002/adom.201700507
  • Optical Properties of 2D Semiconductor WS2
    • Authors: Chunxiao Cong; Jingzhi Shang, Yanlong Wang, Ting Yu
      Abstract: 2D semiconductor tungsten disulfide (WS2) attracts significant interest in both fundamental physics and many promising applications such as light emitters, photodetectors/sensors, valleytronics, and flexible nanoelectronics, due to its fascinating optical, electronic, and mechanical properties. Herein, basic exciton properties of monolayer WS2 are reviewed including neutral excitons, charged excitons, bounded excitons, biexcitons, and the effects of electrostatic gating, chemical doping, strain, magnetic field, circular polarized light, and substrate on these excitonic structures. Besides basic excitonic emission, single-photon emission, exciton–polaritons, and stimulated emission in monolayer WS2 are also discussed. The understanding of these optical phenomena is critical for the development of potential optical applications in electronic and optoelectronic devices. Finally, a summary and future prospective of the challengers and developments regarding 2D semiconductor WS2 is presented.2D semiconductor WS2 shows promising and significant prospects for future optoelectronics and nanoelectronics. A brief overview of recent advances in the optical properties of monolayer WS2 is provided from the aspects of its basic exciton properties including neutral excitons, charged excitons, bounded excitons, biexcitons, and luminescence beyond basic exciton emission such as single-photon emission, exciton–polaritons, and stimulated emission.
      PubDate: 2017-11-17T07:21:27.446308-05:
      DOI: 10.1002/adom.201700767
  • Flexible and Adaptable Light-Emitting Coatings for Arbitrary Metal
           Surfaces based on Optical Tamm Mode Coupling
    • Authors: Alberto Jiménez-Solano; Juan F. Galisteo-López, Hernán Míguez
      Abstract: This study demonstrates a design that maximizes the power radiated into free space from a monolayer of nanoemitters embedded in a flexible distributed Bragg reflector conformably attached to a metal surface. This is achieved by positioning the light source at the precise depth within the multilayer for which optical Tamm states provide enhanced quantum yield and outcoupling efficiency, which are combined to optimize the luminous power radiated by the surface of the ensemble. This approach, based on the adhesion of flexible multilayer stacks onto metal surfaces with an arbitrary curvature, is versatile and permits the realization of spectrally narrow monodirectional or self-focusing light-emitting surfaces.A design that maximizes the power radiated into free space from a monolayer of nanoemitters via optical Tamm states is demonstrated. This is achieved by a conformal attachment of a self-standing distributed Bragg reflector embedding the nanoemitters to a metal surface.
      PubDate: 2017-11-15T05:30:48.494231-05:
      DOI: 10.1002/adom.201700560
  • Utilizing HomoFRET to Extend DNA-Scaffolded Photonic Networks and Increase
           Light-Harvesting Capability
    • Authors: William P. Klein; Sebastián A. Díaz, Susan Buckhout-White, Joseph S. Melinger, Paul D. Cunningham, Ellen R. Goldman, Mario G. Ancona, Wan Kuang, Igor L. Medintz
      Abstract: DNA-based photonic wires that exploit Förster resonance energy transfer (FRET) between pendant fluorophores to direct and focus excitonic energy have high research interest due to their potential applications in light harvesting, biocomputing, and biosensing. One important goal with these structures is to increase their ability to harvest energy and then transfer it over multiple steps both across extended portions of the spectra and physical space. Toward these goals, incorporating extended homogeneous or homoFRET sections into three unique FRET cascade DNA dendrimer architectures are explored. The effects of inserting increasingly longer homoFRET modules into assemblies based on AF488Cy3Cy3.5Cy5Cy5.5 dye-displaying four-arm, eight-arm, and 2:1 dendrimeric DNA photonic wires are evaluated to understand what these hybrid structures may offer toward increased efficiency. Each structure incorporates an extendable Cy3 homoFRET region capable of incorporating one to six Cy3 repeats. Steady-state and time-resolved fluorescence measurements along with detailed analysis and simulations reveal that despite their modest relay capabilities, the structures are capable of acting as efficient antennas, with the dendrimeric structure manifesting a remarkably high sixfold gain. Moreover, an energy transfer efficiency of ≈3% is possible over nine sequential FRET steps.One important goal of DNA-based photonic wires is increasing their energy harvesting and transfer capacity over multiple steps across extended portions of the spectra. Here, homoFRET sections are incorporated into DNA dendrimers. These structures transfer energy over a remarkable nine sequential Förster resonance energy transfer (FRET) steps acting as efficient antennas with the dendrimers manifesting a sixfold gain.
      PubDate: 2017-10-24T11:41:06.983148-05:
      DOI: 10.1002/adom.201700679
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