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Optics and Spectroscopy
Journal Prestige (SJR): 0.319

Citation Impact (citeScore): 1
Number of Followers: 8

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1562-6911 - ISSN (Online) 0030-400X
Published by Springer-Verlag

[2468 journals]

Multi-Band Electrically Controlled Graphene Patch Antenna of the Terahertz
and Far-Infrared Ranges
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  Abstract: The characteristics of a plasmonic graphene patch antenna of rectangular geometry have been simulated in the CST Microwave Studio 2023 software package. It has been shown that the antenna unique property is an electrically controlled multi-band operation (terahertz (THz) and far infrared (IR) ranges) and changing the radiation pattern (RP) toroidal shape to the multi-beam.
  PubDate: 2024-08-11
Parametric Interactions of Waves in Terahertz Devices Based on Graphene
Metamaterials
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  Abstract: The mathematical modeling of operating regimes of parametric THz devices based on graphene metamaterials (graphene‒dielectric periodic structures (GDPSs)) has been carried out by solving a nonlinear 3D diffraction problem for Maxwell’s equations in the projection integral form. Using an algorithm for computing bifurcation points of the nonlinear Maxwell operator, the threshold pump wave amplitudes have been calculated at which an unstable mode of the parametric excitation of electromagnetic waves occurs in GDPS-based THz device.
  PubDate: 2024-07-13
Effect of Doping with Iron and Magnesium on High-Temperature Stability and
Physicochemical Properties of Bismuth Tanalates
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  Abstract: Bismuth tantalum pyrochlores doped with iron and magnesium atoms were obtained thermally stable up to a temperature of 1140°C: Bi2MgxFe1 – xTa2O9.5 – Δ (x = 0–1). The effect of Fe and Mg codoping on their crystal structure has been studied. The unit cell parameter of solid solutions increases uniformly from 10.4871 (2) Å (x = 0) to 10.54607 Å (x = 1). According to the XPS and NEXAFS spectroscopy data, it was found that the ions in these solid solutions are in the charge states Bi(+3), Mg(+2), Fe(+3), Ta(+5 – δ). The dopant atoms iron and magnesium are introduced into the positions of the tantalum atom without distorting the symmetry of the crystal lattice.
  PubDate: 2024-02-01
Simulation of the Interaction of NiO with a Graphene Layer in a NiOx/CNT
Composite Based on XANES Spectroscopy
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  Abstract: The interaction of NiO clusters with a graphene layer of a nanotube in NiOx/CNT composites is simulated based on a theoretical analysis of Ni K-edge XANES spectra. Various cases of orientation of crystallographic planes relative to the nanotube wall are considered. It was determined that Ni in the composite is predominantly in the 2+ state, NiO particles are oriented towards the tube wall by the (200) plane. Accounting for carbon atoms even in the first sphere of the nickel environment makes it possible to achieve good agreement between the theoretical spectrum and experiment.
  PubDate: 2024-02-01
Longwave (λ0.1 = 10 μm, 296 K) Infrared Photodetectors Based on
InAsSb0.38 Solid Solution
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  Abstract: Photodetectors based on diode heterostracture with InAsSbx photosensitive region (x = 0.38) with long-wave cut-off λ0.1 about 10 μm (296 K) are investigated. The dependences of dark current density and detectivity in the temperature range of 200–425 K have been investigated. It is shown that the experimental samples are characterized by values of dark current density about 500 A/cm2 at room temperature, detectivity 1.2 × 109 and 5 × 109 cm Hz1/2 W–1 at room temperature and 250 K, respectively, and diffusion mechanism of current flow in the temperature range 200–350 K.
  PubDate: 2024-02-01
Rotation Angle Sensor Based on a One-Dimensional Photonic Crystal with a
Defect
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  Abstract: The results of numerical simulation of the optical properties of a one-dimensional (1D) photonic crystal with a defect based on semiconductor-dielectric layers in the near-IR range are presented. The simulations used layers of silicon and silicon dioxide with optical thicknesses 3λ/4, λ/4 and 10λ/4. The influence of radiation incident angle on the spectral position of the defect’s guidance band has been studied. It is shown that the sensitivity to the rotation angle lies within the limits of 6–20 nm/deg and 1.7–5.5 dB/deg, depending on the geometry of the sensor and the measurement method. This makes these photonic crystals promising for use in the rotation angle sensors as a sensitive element.
  PubDate: 2024-02-01
Participation of Defects Localized at Heterointerfaces and Extended
Defects in the Degradation of Nitride-Based Light-Emitting Devices
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  Abstract: A decrease in external quantum efficiency (EQE) of commercial LEDs based on MQW InGaN/GaN at wavelengths of 445, 530 and MQW AlGaN/GaN at 280 nm was experimentally studied in the standard aging mode at direct current. The decrease in EQE (regardless of the radiation wavelength) is found out to occur due to cooperative phenomena developing in 1–2 quantum wells (QWs) located in the space charge region (SCR) around the p–n junction, as well as in most of the QWs outside of SCR. It is shown that the inhomogeneous flow of current in these regions leads not only to the transformation of defects localized at heteroboundaries in the SCR and in lateral inhomogeneities in the alloy composition outside of SCR as well as in the extended defects, but also to a change in the alloy composition.
  PubDate: 2024-02-01
Thermal Resistance of LEDs Based on a Narrow-Gap InAsSb Solid Solution
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  Abstract: This paper examines the thermal resistance of the mid-infrared “flip-chip” LEDs based on the p‑InAsSbP/n-InAsSb heterostructure. It was shown that the measurement of thermal resistance via a thermal control unit (forward p–n junction voltage) for LEDs based on narrow-gap semiconductors must be carried out at low temperature when thermal control unit is constant.
  PubDate: 2024-02-01
Collisions of Spin-Polarized Alkali Na and Cs Atoms in the Ground State
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  Abstract: The paper considers collisions involving spin polarized alkali Na and Cs atoms in the ground state. The complex cross sections for spin exchange and the elastic scattering cross sections of the considered atoms are calculated in the energy range from 10–4 to 10–2 a.u.
  PubDate: 2024-02-01
Comparison of the Laser Generation Parameters in the Coherent and in the
Standard Incoherent Passive Mode Locking Regime
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  Abstract: A comparison of the generation efficiency of short pulses with coherent and standard passive (incoherent) mode locking with a saturable absorber is made on the basis of numerical simulations. The advantage of the coherent mode locking in comparison to the standard mode locking in lasers with a saturable absorber is shown. Coherent mode locking in two-section lasers is based on the coherent interaction of the radiation with the absorbing and amplifying media. It allows the generation of ultrashort laser pulses with a duration shorter than the polarisation relaxation time T2 of the absorbing and amplifying media. In conventional lasers with standard (incoherent) passive mode locking with a saturable absorber, the interaction of the laser pulses with the absorbing and amplifying media is incoherent and the duration of the generated pulses is always limited by the polarization relaxation time T2 of the absorber and amplifier.
  PubDate: 2024-02-01
Emission Linewidth and α-Factor of 1.55 μm-Range Vertical-Cavity
Surface-Emitting Lasers Based on InGaAs/InGaAlAs Quantum Wells
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  Abstract: The emission linewidth of single-mode vertical-cavity surface-emitting lasers with an active region based on strained InGaAs/InGaAlAs quantum wells in the spectral range of 1.55 μm was studied. The removal of degeneracy in polarization of the fundamental mode (splitting of the resonance wavelength) and polarization switching (type I) associated with the transition from lasing via the short-wavelength mode to lasing via the long-wavelength one were observed. As the output optical power increased, the emission linewidth dropped to ~30 MHz for both orthogonally polarized modes and was limited by the residual linewidth. The value of the α-factor was estimated: for the short-wavelength mode it reached 5, while for the long-wavelength mode it increased to ~9. At an output optical power of more than 1 mW, the emission line broadening is observed, which can be associated with a gain saturation and the increased α-factor caused by a strong self-heating of the investigated laser.
  PubDate: 2024-02-01
Assessment of Bilirubin Concentrations in the Bile of Patients with
Obstructive Jaundice by Raman Spectroscopy
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  Abstract: Raman spectroscopy (RS) is widely used in biomedicine to detect various chemical compounds in substrates, as well as to determine their concentration. In this work, RS was used to detect bilirubin in the hepatic bile of patients with obstructive jaundice (OJ) of different etiologies obtained via a cholangiostomy drainage catheter. The spectral bands of bilirubin (1258–1264 and 1615–1620 cm–1) were identified using the excitation wavelength of 785 nm. It was found that the assessment of bilirubin in bile allows to predict the recovery of excretory liver function and the dynamics of convalescence of patients with OJ after biliary decompression.
  PubDate: 2024-02-01
Optical Properties of Materials for Magnesium Plasmonics Described within
DFT+U Approach
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  Abstract: The most widely used and applied plasmonic materials, namely silver and gold, has limitations due to their high cost and restriction on the spectral position and shape of the plasmon resonance. This remains true for bimetallic silver–gold nanoparticles. Higher flexibility is required, in particular, for the design of broadband absorbers of light, and for this task the metals other than silver and gold are considered. In this paper we study the optical extinction spectra of alloy and composite nanoparticles containing magnesium and gold. The dielectric properties are calculated within the approximation of independent particles (IPA) based on the electronic structure obtained using density functional theory (DFT) with Hubbard correction (DFT+U). The obtained spectra of optical extinction of magnesium–gold alloy nanoparticles demonstrate that the most sensitive to the composition is the region of wavelengths below 500 nm. Simultaneously, the position of the plasmon resonance predicted by Vegard’s law is higher than obtained from accurate DFT+U based calculations. We managed to describe the experimental optical extinction spectra of the glass sample containing gold and magnesium atoms using the calculated spectra. The results points on the formation of composite nanoparticles with core of Au3Mg alloy and shell of Au in the considered sample.
  PubDate: 2024-02-01
Four-Photon Mixing in a Ghost Fiber Endoscope
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  Abstract: A circuit design of a fiber endoscope is described that allows monitoring of hard-to-reach cavities and other partially transparent and/or reflective objects into which it is possible to pass a thin fiber bundle.
  PubDate: 2024-02-01
Interaction of an Electromagnetic H-Wave with an
“Insulator–Semiconductor–Insulator” Nanostructure in the View of
Semiconductor Band Structure Anisotropy
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  Abstract: The problem of electromagnetic H-wave interaction with a layered “insulator–semiconductor–insulator” nanostructure is solved. We assume that the semiconductor layer thickness can be comparable to or less than the charge carrier de Broglie wavelength. Charge carrier surface scattering is taken into account by the Soffer boundary conditions. The electromagnetic wave frequency is less than the plasma resonance frequency. The constant energy surface is an ellipsoid of revolution. Analytical expressions are obtained for the reflection, transmission and absorption coefficients. Calculations are performed for the limiting cases of a degenerate and nondegenerate electron gas. We analyze the dependences of the optical coefficients on dimensionless parameters: the semiconductor layer thickness, the electromagnetic wave frequency and incidence angle, the chemical potential, the ellipticity parameter, the insulating layer permittivities, and the “semiconductor–insulator” interface roughness parameters.
  PubDate: 2024-02-01
Spectral Properties of Composite Materials Based on Nanoporous High-Silica
Glasses Activated by Silver and Lanthanum Ions
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  Abstract: Spectral properties of composite materials based on matrices of high-silica porous glasses activated by silver ions and lanthanum ions have been investigated. The optical density spectra (270–900 nm) and infrared transmittance spectra (11 000–9000 and 9000–4000 cm–1) of composite materials of different compositions subjected to heat treatment according to one of three modes (120, 500 and 800°C) have been considered. The synthesized composite materials were investigated by X-ray powder diffraction method and energy-dispersive X-ray spectroscopy. The analysis of optical spectra permitted to identify the formation of molecular clusters, clusters, dimers and silver nanoparticles, as well as absorption bands related to charge transfer O2+ → La3+ (282, 285, 300 nm) and to lanthanum nanoparticles (282, 285 nm) under different conditions of synthesis of composite materials. It was found that the change in the mode of thermal treatment of composites leads to changes in the IR spectra of composites, and the change in their composition leads to the appearance of additional bands associated with the oxygen atom of the OH-group, which can coordinate with several neighboring lanthanum atoms.
  PubDate: 2024-02-01
Phonons and Features Due to Ionic Conductivity in the Reflection Spectra
of BiF3 Crystal
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  Abstract: Crystals of bismuth fluoride BiF3 grown from a melt were studied for the first time by optical spectroscopy methods and calculated from first principles in the phonon excitations region. A study of IR reflectance spectra in polarized light was carried out. The parameters of optical phonons were obtained. In the IR reflectance spectra, a low-frequency rise in the range <500 cm–1, characteristic of conductive materials, is observed. The reflection spectra were analyzed within the framework of the Drude–Lorentz model, taking into account the contribution of ionic conductivity. An ab initio calculation of the phonon spectrum of a BiF3 crystal was carried out and the relationship between theoretical and experimental data was analyzed.
  PubDate: 2024-02-01
Chemiluminescent Hydrogen Peroxide Sensor Based on Luminol and a Colloidal
Solution of Metal Nanoparticles
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  Abstract: The effect of gold and silver nanoparticles with plasmon resonance on the chemiluminescence of luminol in an oxidizing environment was studied. It has been shown that when a colloidal solution of metal nanoparticles is added to luminol, the intensity of chemiluminescence caused by the presence of hydrogen peroxide and sodium hypochlorite increases and can be easily recorded at a pH level characteristic of biological media close to neutral, at which chemiluminescence is weak in the absence of metal nanoparticles.
  PubDate: 2024-02-01
Probability of Absorption and Emission by an Atom Interacting with
Ultrashort Laser Pulses
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  Abstract: We consider the process of transition of a two-level system to the excited state with subsequent photon emission in the presence of a laser pulse with a high degree of unipolarity. Within the framework of quantum electrodynamics, we obtain analytical expressions for the differential probability of the process depending on the temporal scales of the problem: laser pulse duration, excited-state lifetime, inverse transition frequency, and inverse frequency of the photon emitted. Besides, we calculate the total absorption probability by integrating over the three-dimensional photon momentum and summing over polarizations. We compare the results obtained for unipolar and bipolar (many-cycle) pulses.
  PubDate: 2024-02-01
Formation of Silver Nanoparticles Oligomers Obtained via Laser Ablation in
a Liquid by Sequential Centrifugation and Ultrasonication: Tunable
Long-Wavelength Shift of Plasmon Resonance for Biomedical Applications
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  Abstract: A relatively simple physical method has been proposed for fabrication of stable oligomers of silver nanoparticles, preliminarily obtained by pulsed laser ablation of a metal target in a liquid. Oligomers of silver nanoparticles are formed in an aqueous solution after prolonged centrifugation at 18 000g and subsequent ultrasonication of the initial colloidal solution of spherical nanoparticles obtained by laser ablation. The plasmon resonance in oligomers is shifted relative to the plasmon resonance in spherical nanoparticles to the long wavelength region by 140 nm.
  PubDate: 2024-02-01

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