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A method for forming p-n-diode based silicon electro-optic modulators using local oxidation is tested. It is shown that the local oxidation of silicon allows forming a waveguide crest shaped as a smoothed trapezoid, in contrast to the classical technique of creating a waveguide crest by plasma-chemical etching. The main advantages of the approach used are described: controllability and reproducibility of critical structural parameters of the modulators (width and height of the waveguide crest), low surface roughness, and the possibility of using approaches to forming a modulating p-n-diode of combined structure in a ridged waveguide, which is standard for planar technologies.

Two types of mirror structures with saturable absorption are under consideration: monolithic mirrors grown from semiconductor materials and mirrors with a dielectric reflector, with quantum well containing semiconductor structures transferred to the dielectric. Both types of mirrors manifest high reflectivity in the near IR range of the spectrum: the "beam table" width is about 100 nm for semiconductor reflectors and more than 200 nm for dielectric reflectors. It is shown that a maximum depth of absorption modulation from 1 to 40 % is possible. The recovery time of the saturating absorber (2 ps) makes these mirrors significantly fit for using in lasers with a pulse repetition frequency of 1 GHz

This paper presents the results of numerical simulation for 43m class crystals and experimental results for azimuthal angular dependences of polarization components of a signal of a second-harmonic reflected from GaAs substrates with (013) orientation, CdTe/ZnTe/GaAs buffer layers, and Cd_xHg_1-xTe/CdTe/ZnTe/GaAs structures, sequentially grown on these substrates with normal incidence of laser radiation on the sample and azimuthal rotation of its polarization plane. It is revealed from investigating the (013)GaAs substrates and CdTe/ZnTe/GaAs buffer layers that deviations from the base cut (013) relative to angles turn out to be 1-3 in the GaAs substrates and up to 8 in the CdTe/ZnTe/GaAs buffer layers. The observed asymmetry of the minima of angular experimental dependences of the second-harmonic signal in the GaAs substrates is related to stresses. It is assumed on the basis of the experimental data that the tensor components of nonlinear susceptibility of the crystalline structure Cd_xHg_1-xTe significantly exceed similar tensor components in CdTe and GaAs in value

The theory of coherent photon-stimulated electron tunneling through a one-dimensional smooth barrier was successfully used to model the results of measuring the terahertz photoconductivity of a tunnel point contact in a two-dimensional electron gas. For this barrier in a deeper tunnel mode, photon steps in the dependence of the tunneling coefficient on the initial electron energy were found. Their position is determined by the energy of the terahertz photon

The relationship of the diffraction efficiencies of volume reflection holograms obtained with the use of double-beam and single-beam recording schemes in absorbing light-sensitive materials is studied theoretically and experimentally. This relationship is demonstrated by an example of a particular photopolymer material.

A system of quantum dots based on Al _x In_{1- x} As/Al _y Ga_{1- y} As solid solutions is investigated. Application of Al _x In_{1- x} As wide-gap solid solutions as the basis of quantum dots substantially expands the spectral range of the radiation to the short-wavelength region, including the wavelength region near ~770 nm, which is of interest for the development of aerospace systems of quantum cryptography. The optical characteristics of Al _x In_{1- x} As single quantum dots grown by the Stranski-Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of radiation of the exciton states of single quantum dots was studied using a Hanbury Brown-Twiss interferometer. The function of paired photon correlations clearly shows the sub-Poissonian character of the radiation statistics, which directly confirms the possibility of developing single-photon emitters based on Al _x In_{1- x} As quantum dots. The fine structure of the exciton states of quantum dots was investigated in the wavelength region near ~770 nm. The magnitude of splitting of exciton states is found to be comparable with the natural width of exciton lines, which is of great interest for the development of emitters of pairs of entangled photons based on Al _x In_{1- x} As quantum dots.

A method for automatic determination of combustion regimes using flame images on the basis of the tagged data of a trained convolutional neural network is under consideration. It is shown that the accuracy of regime classification reaches 98 % on the flame images of a gas burner. The results of the operation of the convolutional neural network and classification using different linear models are compared.

A method for designing Takagi-Sugeno fuzzy systems is proposed in which the structure of the systems is generated using a piecewise linear initialization algorithm, and parameters are optimized using a meta-heuristic algorithm. The obtained systems are tested against real data sets. The influence of some parameters of this algorithm on the approximation accuracy are analyzed. Estimates of the approximation accuracy and the number of fuzzy rules are compared with four known methods of design

This paper describes the problem of passive identification of heat equation coefficients with account for the noise of the behavior of the object dynamics model and for the noise of the measuring system model. The use of the finite difference method allowed for reducing the solution of partial differential equations to the solution of a system of linear finite-difference and algebraic equations described by models in the form of a state space. Presentation of the heat equation in form of such a model makes it possible to apply the Kalman filter algorithm for the reliable estimation of the behavior of the object under study.

Optical (refractive index and absorption coefficient) and thermo-optical (linear thermal expansion and thermo-optic coefficients) characteristics of a new hybrid organic-inorganic photopolymer material "Hybrimer-TATS" based on thiol-siloxane and tetraacrylate oligomers are studied. Variation of the ratio of initial components makes it possible to change the thermo-optic coefficient from -0.7 x 10^-4 to 0,66 x 10^-4 K^-1, which offers prospects for synthesizing athermal optical components and optical elements with a high sensitivity to temperature variation for thermal sensors.