Publisher: Springer-Verlag (Total: 2626 journals)

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 Applied Physics B: Lasers and OpticsJournal Prestige (SJR): 0.74 Citation Impact (citeScore): 2Number of Followers: 27      Hybrid journal (It can contain Open Access articles) ISSN (Print) 0946-2171 - ISSN (Online) 1432-0649 Published by Springer-Verlag  [2626 journals]
• Investigation on response function of terahertz air coherent detection
technique
• Abstract: Abstract Terahertz (THz) air coherent detection is a broadband coherent detection technique, which has been used widely in the THz science and technology. In this paper, a frequency-dependent response function of THz air coherent detection is defined based on the nonlinear polarization of gas molecules induced by the ultrashort laser pulses and the THz pulses. Calculations show that the response function of this technique has a half of Gaussian-like profile, which has a high sensitivity in the low frequency range and low sensitivity in the high frequency range of THz waves. Two fitted functions are given based on the calculated results, which can provide a good reference bandwidth when using the air coherent detection with a given probe laser pulse. The distortions of THz pulses induced by the air coherent detection in the detection process are discussed as well. This study will help to understand the response bandwidth and the limitation of detection bandwidth of the air coherent detection technique.
PubDate: 2020-06-24

• Optical quality of turbulently flowing dye solution
• Abstract: Abstract It is believed for a long time that optical quality of liquid gain-medium (dye solution) of high pulse-repetition-frequency dye laser is degraded by its turbulent flow but so far this belief is not verified by direct experiment. We have devised a novel experiment to study the exclusive effect of turbulent flow on the optical quality of the dye solution pumped by copper vapour laser. The experiment, based on interferometry, shows that the turbulent flow does not degrade the optical quality of the flowing dye solution.
PubDate: 2020-06-22

• Investigation of molecular and elemental changes in rice grains infected

• Abstract: Abstract The primary aim of this work was to study the diseased and healthy rice plant samples at the elemental and molecular level to get the proper understanding of the causes and the chemical changes occurred in the healthy rice grains with the infestation due to false smut disease. We have used microscopic and isolation methods to detect and identify the presence of the species of pathogen involved in the diseased rice plant samples. Elemental analyses of rice grains were carried out using laser-induced breakdown spectroscopy (LIBS) and wavelength dispersive X-ray fluorescence (WDXRF) spectrometry. This revealed the mineral changes appeared in diseased rice plant samples due to the invasion of pathogens. The results from LIBS and WDXRF showed that the mineral elements such as calcium (Ca), magnesium (Mg), silicon (Si), copper (Cu) and iron (Fe) decreased in diseased rice grains than those of healthy rice grains whereas some elements showed their variable behavior in diseased rice grains than those of healthy grains. The results obtained by LIBS is in close agreement with the results obtained by WDXRF. We have employed Fourier-transform infrared (FTIR) spectroscopy to study the molecular changes appeared in the active bio compounds of the rice grains due to the infection caused by false smut. The present spectroscopic studies would provide the proper understanding of the rice false smut disease and also help in developing the proper treatment strategies to prevent the further yield loss caused by the rice false smut disease.
PubDate: 2020-06-22

• Impact of Se doping on optical and third-order nonlinear optical
properties of spray pyrolysis fabricated CdS thin films for
optoelectronics
• Abstract: Abstract Cadmium sulphide is known to have tremendous applications towards optoelectronic and nonlinear devices. Hence, here we have facilely casted the CdS films with diverse Se contents through low-cost spray pyrolysis technique. XRD study defends mono-phase formation of CdS having hexagonal system at all Se doping contents. Scherrer equation was employed to evaluate crystallite size in range of 15–25 nm. Vibrational study reveals the presence of fundamental modes of vibration of hexagonal CdS. EDX and SEM mapping studies approve the existence of Se and its homogeneous distribution all over the film. SEM micrographs shows the nanoscale grains formation on film surface and the size is increasing with Se doping. Optical study revealed that the grown films are of optimal quality with transparency in range of 60–75% with low absorbance and reflectance values. The refractive index values are noted to varied from 1 to 2.7 with wavelength and noticed to be reduced on Se content in UV–Vis region. The reduction in direct and indirect energy gap was found from 2.46 to 2.34 eV and 2.21 to 1.96 eV, correspondingly due to Se. PL emission profile contains an emission band at 528, 529, 529, 530 and 546 nm for 0.0, 0.5, 1.0, 2.5, 5.0 wt% Se:CdS films. Dielectric constant and loss were estimated. The nonlinear refraction (n2) and absorption coefficient (β) and third-order nonlinear susceptibility $$(\chi^{3} )$$ values were determined using Z-scan and observed in order of 10–8 cm2/W, 10–4 cm/W and 10–3 esu, correspondingly. The high values of $$\chi^{3}$$ propose the films for nonlinear applications.
PubDate: 2020-06-15

• Tunable converge optical elliptical vortex based on elliptical helical
lens
• Abstract: Abstract We present a new scheme to produce a tunable converge elliptical optical vortex (EOV) with a phase-only element: elliptical helical lens (EHL), which is studied theoretically and experimentally. As a result, the properties of converge EOVs can be controlled by adjusting the parameters of EHL. The topological charges of the EOVs can be directly read from the received intensity pattern. Because EHL is a hologram programmed in space light modulator (SLM), converge EOVs can be controlled just by reprogramming the SLM instead of replacing actual instruments. This work has potential applications in particle manipulation, as well as generation of OAM-entangled photons.
PubDate: 2020-06-12

• Dielectric slotted nanodisk laser with ultralow pump threshold by anapole
excitation
• Abstract: Abstract Developing ultralow threshold nanolasers is a challenging task despite of their great potential for a variety of applications. This work proposes to combine the advantages of low loss of dielectric materials and tight confinement of field in slotted dielectric nanodisks with gain medium embedded to them and supported by metallic substrate, which generates anapole mode with a lifetime longer than for dielectric substrate. Since the dielectric nanocavity has intrinsically low loss, one can achieve lasing with ultralow threshold down to 0.02 pJ for a spot size 1.5 μm of pump, several orders-of-magnitude lower than the preceding records. Dielectric slotted disk nanolasers proposed here can find broad applications for biosensing, near-field spectroscopy, and many other fields.
PubDate: 2020-06-11

• Design and simulation of a compact and ultra-wideband polarization beam
splitter based on sub-wavelength grating multimode interference coupler
• Abstract: Abstract A compact and ultra-wideband multimode interferometer (MMI)-based polarization beam splitter (PBS) is designed in a silicon-on-insulator (SOI) platform. A sub-wavelength grating (SWG) structure is employed in the multimode region to reduce the overall length of the structure and also increase its operating bandwidth. Instead of using the beat-length difference to separate the transverse electric (TE) and transverse magnetic (TM) polarized waves, the TM waves are directly coupled to the output bar port through an interconnecting waveguide, while the TE polarized waves are transmitted to the cross port by the self-imaging process. This substantially reduces the length of the PBS and the overall footprint can be as small as 4.8 × 21 µm2. The proposed device exhibits the extinction ratio of more than 15 dB in a 250 nm wavelength range (1.38–1.63 µm) and more than 12 dB in the 350 nm wavelength range (1.3–1.65 µm) for the TE and TM polarizations, respectively. In addition, the insertion loss remains below 1.2 dB for both the TE and TM polarization in a broad wavelength range from 1.38 to 1.54 µm. The proposed PBS can be fabricated by a single-step etching process on an SOI wafer. Moreover, our simulations show the robustness of the PBS performance to the fabrication errors’.
PubDate: 2020-06-09

• First demonstration of ~ 5 µm laser action in
terbium-doped selenide glass
• Abstract: Abstract 4.9–5.5 µm laser oscillations were observed in high-purity bulk terbium-doped Ge36Ga5Se59 glass pumped by pulsed 2.93 µm Er:YAG laser. This is the first evidence of laser action corresponding to 7F5–7F6 transition of Tb3+ ions and of mid-infrared lasing in chalcogenide glass host.
PubDate: 2020-06-09

• A bidirectional reflectance distribution function model of space targets
in visible spectrum based on GA-BP network
• Abstract: Abstract An optimized Back-Propagation network (BP network) based on Genetic Algorithm (GA) was introduced to construct bidirectional reflectance distribution function (BRDF) model. To verify the performance of GA-BP network, two different kinds of space target materials were used for experiment. Based on the experimental data, we used GA to simulate the undetermined parameters of a five-parameter BRDF model, and used GA-BP network and BP network to construct a new BRDF model respectively. The fitting results manifest that the GA-BP network is suitable for construct a new BRDF model and outperforms the five-parameter BRDF model in speed and accuracy under the same condition.
PubDate: 2020-06-04

• Negatively chirped pulse compressor with internal telescope for
1.4 µm range
• Abstract: Abstract The peculiarities analysis in design of compressors for negatively chirped optical pulses parametrically amplified in double-chirped regime up to 1 J in multi-cascade system is done. A comparative analysis of the spatio-temporal distribution of the pulses at the output of various compressor schemes with an internal telescope has been performed. The analysis has been carried out using two methods: calculating additional compressor dispersion using the Seidel aberration coefficients of the internal telescope and the ray tracing method. A ray-tracing algorithm has been developed that allows to calculate the spatiotemporal and spatiospectral pulse intensity distributions at the output of compressors with an internal telescope. The on-axis and off-axis Offner schemes, Martinez scheme compressor and compressor scheme with a single-lens internal telescope are analyzed. It is shown, that the ray tracing method more accurately takes into account system aberrations, including high-order aberrations, while the calculation with the Seidel aberration coefficients takes into account only primary aberrations. According to the analysis, the optimal scheme of a grating compressor with an internal telescope for compressing negatively chirped pulses in the range of 1410 nm to a duration of less than 40 fs and energies up to ~ 0.8 J is the off-plane Offner scheme.
PubDate: 2020-06-04

• All-passive optical diode using living liquid crystal doped with silver
nanorods
• Abstract: Abstract Some industrial uses of living cells involve genetic engineering or modification of cell’s external properties. However, these techniques commonly have high financial costs, do not take advantage of the natural properties of the cells, and have few applications in the photonics area. As the first technological application of living liquid crystals, we propose an all-passive optical diode using Bacillus subtilis, chromonic liquid crystal, and silver nanorods. These three elements comprise a living liquid crystal doped with nanorods that produces a spatial inversion asymmetric system, facilitating the passage of light in one direction and hampering it in the opposite one. Solving Maxwell’s equation numerically for this system, we found optical rectification for light’s intensity up to $$1700\%$$. Such diodes can be the primary units for an all-passive optical film and other nonreciprocal systems.
PubDate: 2020-06-04

• Identification of metals and alloys using color CCD images of
laser-induced breakdown emissions coupled with machine learning
• Abstract: Abstract We demonstrate here, for the first time to the best of our knowledge, the method of classification and identification of metals, metal alloys using the color CCD images of femtosecond (fs) laser-induced plasma emissions. The non-gated color CCD images of the plasma emissions were used to train the machine learning algorithm for identification. We have also compared the obtained results with the fs-laser-induced breakdown spectroscopy (LIBS) results. The green channel in the RGB image was used for the classification and prediction of metals and metal alloys. The present work explores the possibility of identification of the aluminum, copper, bronze, and steel using a simple instrument such as the CCD. Each sample formed extended clusters in the classification performed using principal component analysis (PCA). The extracted features from the PCA were used as input to train the support vector machine (SVM) and for prediction and the results are intriguing.
PubDate: 2020-06-03

• Mode evolution mechanism of Pr 3+ :YLF single longitudinal mode laser
• Abstract: Abstract We develop a theoretical model of multimode rate equation that accurately describes mode evolution mechanism of prelase Q-switched Pr3+:YLF single longitudinal mode (SLM). We find that it is important to consider the effect of gain difference when calculating the mode competition time accurately. We identify that there is an optimal parameter for the two step signal of acoustic-optic modulator which determines the stability of SLM output. Then, a visible light direct oscillation Q-switched SLM Pr3+:YLF laser at 639.5 nm is obtained, and the experimental results is agree with the simulation very well.
PubDate: 2020-06-02

• Fabrication of optical nanofibre-based cavities using focussed ion-beam
milling: a review
• Abstract: Abstract Nanofibre-based optical cavities are particularly useful for quantum optics applications, such as the development of integrated single-photon sources, and for studying fundamental light–matter interactions in cavity quantum electrodynamics (cQED). Although several techniques have been used to produce such cavities, focussed ion beam (FIB) milling is becoming popular; it can be used for the fabrication of complex structures directly in the nanofibre. However, it is challenging to mill insulating materials with highly curved geometries and large aspect ratios, such as silica nanofibres, due to charge accumulation in the material. In this article, we highlight the main features of nanofibres and briefly review cQED with nanofibre-based optical cavities. An overview of the milling process is given with a summary of different FIB milled devices and their applications. Finally, we present our technique to produce nanofibre cavities by FIB milling. To overcome the aforementioned challenges, we present a specially designed base plate with an indium tin oxide (ITO)-coated Si substrate and outline our procedure, which improves stability during milling and increases repeatability.
PubDate: 2020-05-31

• Temporal dynamics of resonant scattering of an ultrashort laser pulse by
an atom
• Abstract: Abstract Within the framework of the second order of perturbation theory and the dipole approximation, we derived simple formulas describing the temporal dynamics of ultrashort laser pulse scattering in terms of the scattering tensor and the Fourier transform of the strength of the electric field in a pulse. This expression was used for description of resonant scattering of an ultrashort pulse by an atom. We study the dependence of the spectral scattering probability as a function of time and scattering frequency. In particular, it is shown that the time dependence of the spectral scattering probability for certain values of parameters is of oscillatory character, while the integral scattering probability is always a monotonically increasing function of time.
PubDate: 2020-05-26

• Full-field refractive index measurement using absolute-phase total
internal reflection heterodyne interferometry
• Abstract: Abstract In this paper, absolute-phase total internal reflection heterodyne interferometry is proposed for measuring a full-field refractive index. In this method, an optical configuration of prism-based total internal reflection is used. If an electro-optical modulator is driven by a sawtooth wave with an amplitude lower than the half-wave voltage, heterodyne interferometric signals can be generated in segment mode. After a camera has captured these discrete interferometric signals, the optimum signal segment can be analyzed; a specific time segment can be inserted so that the interferometric signals of every pixel can be fitted as a continuous sinusoidal wave; a least-squares sine-fitting algorithm can extract the initial phase. Finally, the absolute phase can be calculated by subtraction of the characteristic phase, and the full-field refractive index can be obtained. To prove the feasibility of the proposed method, the different combinations of specimens were measured, including air, water, glycerol, and castor oil. The experimental data correspond well with the theoretical values. This method features simple operation, low influence of environmental disturbance, rapid measurement, and high resolution.
PubDate: 2020-05-24

• Large tunable lateral shift in prism coupling system containing a
superconducting slab
• Abstract: Abstract A large and tunable lateral shift in a prism coupling system with a superconducting YBa2Cu3O7 film is theoretically analyzed. The dip of the reflectivity and magnitude of the lateral shift can be controlled by the temperature of the superconducting film. The sign of the lateral shift can be determined by the thickness of the superconducting film. The position of the minimum reflection and maximum Goos–Hänchen shift can be conveniently adjusted by the thickness of the dielectric layer and incident light frequency. The largest shift, as high as 1550 times the free space wavelength, is achieved for the incident light frequency $$\omega = 98$$ THz. The numerical calculation results from the Gaussian beam are in accordance with the theoretical results.
PubDate: 2020-05-23

• Laser-induced incandescence
• PubDate: 2020-05-22

• Long-term stable 850-Hz linewidth single-longitudinal-mode ring cavity
fiber laser using polarization-maintaining fiber
• Abstract: Abstract A long-term stable single-longitudinal-mode (SLM) all polarization-maintaining (PM) compound-ring cavity fiber laser is reported. The results show that the PM fiber's strong ability to resist the environment disturbance allows finely designing the length of each secondary cavity in real time according to the main cavity under the laboratory environment, and then the effective longitudinal mode spacing can be sufficiently increased by accurately using the Vernier effect, so that the mode-hopping can be effectively suppressed. Furthermore, the temperature compensation is used for asynchronously fine-adjusting each cavity length to follow the Vernier effect requirement more strictly. The mode-hopping-free SLM operation time of the packaged laser reaches 11 h. As far as we know, this is the longest SLM free running time of ring cavity fiber laser to date. The optical signal to noise ratio of the laser reaches 77 dB and the linewidth is less than 850 Hz with up to 50 mW maximum output power.
PubDate: 2020-05-21

• MW peak-power UV inductive nitrogen laser
• Abstract: Abstract For the first time, the UV inductive nitrogen laser was created with generation energy of 11 mJ and pulse duration 10 ± 1 ns (FWHM). Lasing was obtained on two lines with wavelengths of 337.1 and 357.7 nm. The generation energy distribution over the cross section had a shape of a ring with diameter and width of about 40 and 2 mm, respectively.
PubDate: 2020-05-20

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