Subject of study. A two-channel optical system for vein morphology imaging and projection of binary vein maps onto the skin surface is studied. Aim of study . The aim of this work is to develop an optical system for a universal device for noninvasive vein detection and visualization, including multispectral image acquisition. Method . Synthesis of the base optical system was based on the algebraic synthesis method. Parametric synthesis was then performed by mathematical optimization of the design parameters. Main results . A two-channel optical system with a shared optical element and negligible geometric image distortions is proposed. The choice of illumination wavelength for the registration channel was verified. A multispectral design of the registration channel capable of acquiring spectral images in snapshot mode is proposed. A methodology for dimensional synthesis, including the design of the multispectral registration channel, was developed and used to design the complete optical system. Practical significance . The proposed two-channel system can be used in a variety of medical applications requiring visualization of vein morphology, including detection of vascular obstructions and preoperative preparation. When combined with effective algorithms for calculating multiwavelength index images, the multispectral design enables reliable vein morphology imaging in patients with darker skin tones.
Subject of study . Circuit design solutions for a quantum key distribution system implemented on unmanned aerial vehicles are investigated. Aim of study . The aim is to develop a compact and energy-efficient quantum key distribution system, adapted for installation on unmanned aerial vehicles, and capable of stable key generation under atmospheric optical signal propagation. Method . Computer simulation of optical circuits and modeling of flight conditions, including turbulence and atmospheric interference, are used to assess noise immunity, particularly emphasizing efficiency under limited resource conditions. Main results . An atmospheric optical scheme for implementing the BB84 protocol with decoy-state technology is proposed. A two-pass tracking system for stable alignment and synchronization under movement and vibrations is developed. In addition, optimal aperture parameters (diameter 4–7 cm) for operation at distances of up to 1000 m are determined. Practical significance . The developed solutions enable the creation of a mobile quantum key distribution system for rapid deployment in hard-to-reach areas. The compact size and low power consumption of the system make it compatible with small and medium unmanned aerial vehicles, thereby expanding opportunities for secure communication in emergency situations, remote-area monitoring (e.g., forest fires and floods), agriculture, and infrastructure protection.
Subject of study. The polarization characteristics of scattered solar radiation in the presence and absence of high-level clouds (HLCs) are investigated. Aim of study. The aim is to develop a technique for detecting and identifying HLCs containing horizontally oriented ice particles based on passive measurements of the polarization characteristics of scattered solar radiation at the zenith. Method. The polarization characteristics of scattered solar radiation obtained from passive (polarimetric) measurements are analyzed in conjunction with the optical and geometric characteristics of HLCs determined simultaneously from active polarization (lidar) observations. Main results. Polarimetric measurements of scattered solar radiation at the zenith, performed with simultaneous monitoring of the atmospheric aerosol state, including HLCs, using a matrix polarization lidar, are presented. Under clear-sky conditions, the expected consistency between the polarization degree of scattered solar radiation and the solar zenith angle is observed. In the presence of HLCs, deviations from a smooth diurnal variation caused by the multilayer cloud structure are revealed. Practical significance. The results confirm the feasibility of using passive polarimetry for diagnosing the state of cloud cover and atmospheric aerosol layers. They also demonstrate the need for the further development of polarimetric methods and their integration with active atmospheric sensing techniques. Improvement of these methods will contribute to increased accuracy in climate research.
Subject of study. The optical characteristics of high-level clouds (HLCs), which significantly affect the Earth’s radiation budget and climate due to their large spatial extent, are investigated. Aim of study. This study aims to develop an approach for the comprehensive study and assessment of HLC characteristics. In addition, the study seeks to determine the conditions and frequency of HLC occurrence by comparing satellite, lidar, and meteorological data, thereby broadening the geophysical applicability of the results. Method. Data from polarization lidar sensing, the MODIS satellite spectroradiometer, radiosonde observations, weather stations, and atmospheric reanalysis datasets ERA5 and MERRA-2 are used. These reanalysis datasets combine numerical atmospheric modeling with heterogeneous observations, providing temporally and spatially consistent datasets. Main results. A lidar dataset for 2009–2024 is described, together with the distributions of HLC characteristics derived from it. Atmospheric data sources suitable for predicting the formation of HLCs and their characteristics, including cirrus with a preferred horizontal orientation of ice crystals, are identified. Practical significance. The results can be used to refine parameters in climate models and short-term cloud forecasts, as well as for analyzing the distribution and dynamics of clouds in various regions. Integration of local lidar observations with large-scale meteorological information based on the analysis of optical characteristics of clouds significantly expands the geophysical applicability of the results.
Subject of study. The determination of the parameters of gradient waveguides required for the fabrication of integrated optical circuits with low optical losses is presented. Aim of study . This work aims to develop a new approach for determining all key parameters of gradient proton-exchanged waveguides in single crystals and solid solutions. Method . Confocal Raman microscopy, the prism coupling method, and a numerical solution of the classical transport equation are used to reconstruct gradient waveguide profiles. Main results. Gradient profiles of proton-exchanged waveguides formed in lithium niobate crystals and lithium niobate–tantalate solid solutions of X - and Z -cuts are reconstructed by measuring the OH-group line in the Raman spectrum. The reconstructed profiles are in good agreement with those obtained by the prism coupling method and diffusion theory, enabling accurate determination of the waveguide layer depth. The refractive index increment is determined from a calibration curve calculated in this work that establishes the relationship between the Raman scattering intensity in the OH-group region and the refractive index increment. This approach allows the estimation of all the main parameters of proton-exchanged waveguides at any point, which is not achievable using conventional methods. Practical significance. The results can be applied for the rapid nondestructive characterization of gradient proton-exchanged waveguides in integrated photonics devices.
Subject of study . Zinc oxide nanoparticle coatings are investigated. Aim of study . This work aims to develop an effective technology for producing antibacterial coatings using the laser-induced backward transfer method by optimizing the laser radiation and scanning system parameters. Method . The laser-induced backward transfer method is used to fabricate the coating. Optical and scanning electron microscopy are used to characterize the coating topography in conjunction with probe microscopy. Nanoparticle sizes are analyzed by dynamic light scattering. Main results . Depending on the transfer regime, both hydrophilic and hydrophobic coatings composed of zinc oxide nanoparticles with sizes ranging from 16 to 458 nm are obtained. The coatings exhibit antibacterial activity against the Gram-negative bacterium Pseudomonas aeruginosa. Investigation of bacterial viability using the LIVE/DEAD BacLight staining kit confirmed the results of microbiological culture analysis. Practical significance . Zinc oxide nanoparticle-based coatings may serve as a basis for the development of antibacterial agents against a wide range of pathogenic microorganisms.
Subject of the study. The spatial resolution of functional images reconstructed by solving the electroencephalography (EEG) inverse problem is investigated. Objective of the work . This study aims to develop a method for increasing the spatial resolution of functional images and for optimizing the selection of image reconstruction algorithms using metrics derived from statistical analysis of neural activity distributions. Method . Modeling of the solution of the inverse EEG problem was performed using the MNE-Python library in Python. A computational experiment was designed using EEG and functional magnetic resonance imaging data to verify the proposed methodology. Main results . A method for integrating spatial filtering into neuroimaging algorithms was developed, enabling a twofold improvement in the spatial resolution of a functional image using only functional EEG data. In addition, a metric for assessing the spatial resolution of a neuroimaging method was proposed, allowing unambiguous selection of the most appropriate algorithm for functional image processing. Practical significance . The proposed spatial filtering approach makes it possible to distinguish sources of electrophysiological activity separated by approximately 20 mm. The developed image quality criterion enables the selection of the optimal image processing algorithm for a specific application problem.
Subject of study. Optical radiation scattered by a periodic structure of microcavities formed in a planar optical waveguide simulating a 62.5/125 µm multimode fiber is investigated. Aim of study. This work aims to determine the power distribution of optical radiation scattered by a periodic structure of bullet-shaped microcavities on the lateral surface of a planar waveguide based on mathematical modeling, to develop a method for assessing the efficiency of scattering elements, and to determine the values of the geometric parameters of the microcavity structure that yield the highest uniformity of scattered radiation. Method. Mathematical modeling of radiation scattering by a periodic structure is carried out using the COMSOL Multiphysics package. The model allows variation of the size and relative arrangement of the microcavities. Main results. The power distribution of scattered radiation at a wavelength of 1310 nm from the lateral surface of the waveguide is obtained. The results demonstrate that both the size and relative arrangement of the microcavities have a significant effect on the power distribution of scattered radiation. A method for estimating the uniformity of the scattered power distribution along the waveguide is proposed. Practical significance. The results are applicable to multimode optical fibers incorporating periodic microcavity structures for scattering laser radiation. Such fibers can serve as radiation sources for medical applications. Periodic structures can be used as sensing elements for fiber-optic sensors. The results are relevant to the development of diffusers with highly uniform scattered radiation patterns.
Subject of study. A narrow-linewidth, broadly tunable mid-infrared (IR) parametric light source is investigated. The source consists of a singly resonant optical parametric oscillator (OPO) and an optical parametric amplifier (OPA) based on zinc germanium diphosphide nonlinear optical crystals, pumped by a repetitively pulsed Ho 3+ :YAG laser. Aim of study. This work aims to develop a source for generating broadly tunable repetitively pulsed mid-IR radiation with a narrow spectral linewidth and high pulse energy. Method. Narrow-linewidth OPO operation is achieved using an intracavity Fabry–Pérot etalon in the form of a silicon wafer with a thickness of 33 µm or 56 µm. Wavelength tuning in the mid-IR range is realized by varying the temperature of both the etalon and the nonlinear optical crystal. An OPA is employed to increase the pulse energy. Main results. Narrow-linewidth operation of the parametric source with a signal linewidth of 3–8 nm is demonstrated. Tuning is achieved over the ranges of 3860–4130 nm and 4210–4565 nm for the signal and idler waves, respectively. At a repetition rate of 10–50 Hz, the pulse energy reaches 1.7 mJ for narrow-linewidth radiation and 4.8 mJ in broadband (frequency-comb) operation. Practical significance. This high-power narrow-linewidth radiation source that is tunable over the range of 3.8–4.6 µm has potential applications in remote environmental monitoring, particularly for the detection of greenhouse gases such as CO 2 and CO, as well as in wireless optical communication and in selective interaction with materials such as silicon and diamond.
Subject of study. The optical design of an autocollimation tube for measuring lens decenter is investigated. Aim of study. The aim is to develop a compact optical system for measuring the decenter of single lenses, to estimate the measurement error while accounting for the characteristics of the optical system and the use of simple image processing methods, and to analyze the factors influencing measurement accuracy. Method. In the proposed system, the image formed by a surface with a known decenter is modeled within the framework of geometrical optics. The centroid of the intensity distribution is determined using the center-of-mass algorithm, and then used to calculate the decenter of the lens surface. Main results. A compact optical system for lens decenter testing has been developed. The reasons for increased measurement error for lenses with small radii of curvature (20 mm or less) are analyzed in detail. A systematic error affecting the accuracy of decenter determination is identified. After accounting for optical system aberrations, digital image registration, image processing, and the identified systematic error, the residual error in decenter measurements does not exceed 1 µm. Practical significance. The proposed optical scheme can serve as the basis for a production instrument integrated into optical manufacturing equipment. The analysis of error sources in the lens decenter testing system, as well as the applied modeling and processing techniques, is of practical interest for the development of modern high-precision instruments.
Subject of study. A review of circuit design solutions for multiplexers used in wireless optical communication systems to increase the communication channel capacity is presented. Aim of study. The relationships between the parameters of a wireless optical communication system and the circuit solutions of a multiplexer subsystem that are optimal in terms of increasing the communication channel capacity and efficient use of the channel bandwidth are determined. Method. The increase in the capacity of a wireless optical communication system is achieved by adding a multiplexing subsystem to its structure. Optimal multiplexing schemes are determined as a result of an analytical review of various wireless optical communication systems by comparing their parameters and characteristics given in literary sources. Main results. Based on an analytical review of literary sources, which present the results of computer and physical modeling of wireless optical communication systems, multiplexing schemes have been identified, the use of which allows the throughput of an optical communication channel to be increased. Practical significance. The results of the conducted review allow, when designing a wireless optical communication line, the optimal multiplexing scheme for a given application to be selected and, accordingly, the transmission capacity to be increased and the channel bandwidth to be effectively used, satisfying the ever-growing demands of applications that require large volumes of transmitted data. (c) 2026 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Subject of study. An acousto-optic (AO) focusing device using linearly frequency-modulated ultrasonic waves is studied. Aim of study. The parameters of the AO focusing device are determined to estimate the aberrations introduced by it. Method. AO interactions in the low-diffraction-efficiency regime are modeled numerically. Main results. A model that accounts for the length of the AO interaction and the diffraction effects is developed. The results show that the focal spot is a narrow strip with a strongly asymmetric structure, and the wavefront within the spot is tilted by approximately 4 degrees relative to the wavefront of the incident beam. In the case of oblique incidence of radiation on the focusing device, the spot size reduces by a factor of approximately 2; that is, it reduces to 17 & micro;m at the 84% level of the energy concentration function. Further, the focal spot structure becomes symmetric. Practical significance. The obtained results can be used in the development of adaptive optical systems. (c) 2026 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Subject of study. The effect of annealing in a nitrogen atmosphere on the optoelectronic characteristics and surface morphology of indium tin oxide (ITO) thin films is studied. Aim of study. The preparation conditions for ITO thin films with tailored optoelectronic and morphological characteristics are optimized by varying the film thickness and via thermal treatment at 200 degrees C in a nitrogen atmosphere. Method. The optical properties of the films, including light transmittance and haze, are investigated by spectrophotometry. The electrical characteristics are measured using the four-probe method to determine the sheet resistance. Atomic force microscopy is used to examine the surface morphology and thus measure the surface roughness and determine the grain size via autocorrelation analysis. Main results. Thermal treatment in a nitrogen atmosphere improves the optoelectronic characteristics of ITO coatings. The calculated figure of merit confirms that the light transmittance increases, whereas the surface resistance decreases. Morphological analysis reveals that upon increasing the film thickness, the grain size decreases, whereas the grain density increases owing to the activation of diffusion and nucleation processes. Practical significance. The obtained results confirm the effectiveness of using thermal treatment in a nitrogen atmosphere as a viable method for improving the characteristics of ITO coatings, thereby expanding their applicability in optoelectronic devices requiring high transparency, low resistance, and structural stability. (c) 2026 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Subject of the study. This study investigates an optical waveguide based on a one-dimensional three-periodic magnetophotonic crystal composed of dielectric and ferrite garnet layers magnetized to saturation. Aim of the study. The study aims to determine the frequency regions in which hybrid modes exist and to establish the polarization structure of guided modes in a magnetophotonic waveguide. It also examines the influence of 180 degrees magnetization reversal and the demagnetization of magneto-optical layers on the shape of the dispersion spectra. Method. The study employs the 4 & times; 4 transfer-matrix method. Main results. The influence of the parameters of magnetic and nonmagnetic layers (including the number of subcell periods and bigyrotropy) on the dispersion spectra of the eigenwaves of a photonic-crystal waveguide is analyzed. The results show that the magnetization of the layers leads to the formation of hybrid modes from the TE-and TM-polarized modes of the unperturbed structure. This magnetization also produces convergence regions between neighboring dispersion curves and causes a noticeable frequency shift (approximately 9 & times; 109 rad/s) in the propagation constant of the waveguide modes relative to the corresponding values in the demagnetized state of the system. Practical significance. The findings can be applied to the design of new magneto-optical devices based on three-periodic photonic crystals operating in the infrared range, such as narrowband tunable filters and beam formers for laser diodes used in optical communication systems. (c) 2026 Optica Publishing Group
Subject of study. The dynamics of photorefractive hologram formation in Cu:LiNbO 3 structures, fabricated via the thermal diffusion doping of copper ions into lithium niobate crystals, is investigated. Aim of study. The aim of this study is to synthesize Cu:LiNbO 3 samples with enhanced photovoltaic properties for practical applications. Methods. Thermal diffusion doping was performed from 800-nm-thick copper films at temperatures of 600°C and 700°C in an argon atmosphere for 12 h. The concentrations of the Cu + and Cu 2+ ions were determined by optical absorption measurements at wavelengths of 532 and 808 nm, respectively. Photorefractive holograms were recorded, and the temporal evolution of the diffraction efficiency was measured using laser beams with wavelengths of 532 and 650 nm. Main results. Thermal diffusion at 700°C results in the maximum concentrations of donor and trap centers near the X-faces of the crystal plate. The photorefractive holograms formed in these structures exhibit a diffraction efficiency of approximately 0.22 at a grating period of 10 µm (recording time: approximately 100 s). Practical significance. The obtained Cu:LiNbO 3 structures are promising for devices exploiting the evanescent fields of dynamic photorefractive holograms, including hybrid “liquid crystal/Cu:LiNbO 3 ” components and photovoltaic tweezers used for the manipulation of micro- and nano-objects.
Subject of study . Axial computer-generated hologram optical elements (CGHOEs) and laser holographic interferometry based on CGHOEs are studied. Aim of study . The aim of this review is to actualize the original technical solutions developed since the mid-1960s at all stages of the evolution of axial computer-generated hologram optics and laser holographic interferometry (as its derivative). Method . The study is based on the systematization and evaluation of a novel technology of forming periodic ruled structures in the thin working layer of a hologram using a diamond edge tool with a bicylindrical cutting edge. The study is primarily focused on the influence of the off-duty ratio, kinoform profile accuracy, congruence of the recorded structure, and resulting diffraction efficiency. Main results . The main stages of the origin, formation, and development of axial computer-generated hologram optics and laser holographic interferometry at JSC “NPO GIPO” are presented, along with promising options for their further practical implementation. The exceptionally high practical relevance of axial (Gabor-type) holographic testing schemes is demonstrated, highlighting the utility of using axial computer-generated holograms as optical references and null correctors. Several original interferometric system designs employing axial CGHOEs as optical compensators (null correctors), optical samples, and beam splitters are described. In addition, an unequal-arm Michelson interferometer is proposed for simulating the possible cosmological “aging” of light. Practical relevance . The results of this review contribute to the broader adoption of laser holographic interferometry, based on axial computer-generated hologram optics, in optoelectronic instrument engineering.
Subject of study. The study focuses on CsPbBr 3 perovskite nanocrystals (NCs) localized in a quadrupole electrodynamic trap. Aim of study. The aim was to establish the dependence of the photoluminescence spectral characteristics of perovskite NCs on their localization environment, specifically in a colloidal solution and quadrupole electrodynamic trap. Method. Perovskite NCs were delivered to the trap using the “paper spray” electrospraying technique. Spraying from paper cartridges was induced by applying a direct current to the cartridges. Spectroscopy of the localized particles was performed under ultraviolet laser excitation using a monochromator and detector. Main results. The photoluminescence spectra of the perovskite NCs were obtained both in a colloidal solution and when they were localized in a quadrupole electrodynamic trap. A dependence was observed; the photoluminescence spectrum of the localized perovskite NCs was narrower than that of NCs in the colloidal solution. Practical significance. The results obtained in this study serve as a foundation for detailed analyses of the influence of various parameters, such as the particle size, shape, surface states, chemical composition, geometric orientation, and surrounding environment, on the optical properties of nanomaterials.
Subject of study. This study investigates free AgInS 2 and AgInS 2 /ZnS quantum dots and quantum dots encapsulated in albumin nanoparticles (ANPs). Aim of study. The aim of this study is to determine and compare the fluorescence properties and reactive oxygen species-generation abilities of free quantum dots and quantum dots encapsulated in ANPs for their use as photosensitizers (PSs) in photodynamic therapy (PDT). Method. The quantum dots were synthesized using a hydrothermal method, and the ANPs were obtained by the desolvation method. The quantum dots were encapsulated into the ANPs by co-incubation in aqueous solution. The efficiency of superoxide generation was evaluated using a selective chemical sensor. Main results. Growing a ZnS shell on AgInS 2 quantum dots increased both their fluorescence quantum yield and efficiency of superoxide generation. The encapsulation efficiencies of AgInS 2 and AgInS 2 /ZnS quantum dots in ANPs were 60% and 20%, respectively, and they were accompanied by a hypsochromic shift in the fluorescence spectra of the quantum dots. Encapsulation of the quantum dots in ANPs led to a decrease in superoxide-generation efficiency compared with free quantum dots; however, this reduction may be compensated for by their greater stability in biological systems. Practical significance. The findings of this study on the photophysical properties of AgInS 2 quantum dots demonstrate the high potential of nanoplatforms based on quantum dots and ANPs as PSs for PDT.
By decision of the Editorial Board of Opticheskiĭ Zhurnal, Il’ya A. Levin, Tatiana Yu. Fisenko, Svetlana N. Khonina, and Vladimir E. Yashin are recognized as the Best Reviewers of 2024.
