SCIENCE & EDUCATION

The authors investigated conversion of broadband infrared radiation in lithium niobate crystal of stoichiometry and congruent compositions at noncritical 90°- phase-matching condition for vector interactions of light waves. It was shown that conversion efficiency, spectral width and position of the spectrum maximum of the converted broadband radiation depend on the ratio R = Li /Nb in the crystal of lithium niobate. The authors proposed to use the dependence of spectrum maximum of the converted broadband radiation on the composition and structure of crystal as the exact experimental criterion to determine the ratio R = Li/Nb in the crystal of lithium niobate.

This work covers the study of basic characteristics and parameters of optical fiber Bragg gratings (FBG). The paper describes the main theoretical calculation methods of FBG spectral reflection and transmission coefficients and shows FBG reflection spectra measured in two different ways: by using a spectrum analyzer and a broadband pump source, and also by newly created units. The authors compared the theoretically calculated reflection spectra with the experimentally obtained by two different methods.

The atmosphere is one of the basic factors worsening the quality of optical systems. The atmosphere as a medium for radiation propagation shows its distorting influence through the ability to absorb, to scatter, to refract (atmospheric refraction) this radiation, to change its properties continuously (atmospheric turbulence), and also, depending on the state of the atmosphere, to produce different electromagnetic effects (electrical breakdowns, ionization, etc). The author proposes a new approach to examination of the influence of the atmosphere on image quality. It was shown that this influence has geometric and three-dimensional temporary special features. Recommendations regarding effective reduction of this influence are given.

Main mirror is the most complex and expensive part of the contemporary telescope. Its surface must keep its form with accuracy up to small fractions of wavelength with any working inclinations of mirror in entire working temperature range. In this case it must be maximally facilitated in order to ensure acceptable requirements for the framework of telescope.Today, perhaps, there is no doubt that composite mirrors only will be used as the main mirrors of telescopes of the fifth generation; their mutual attitude of separate elements during the work will be continuously corrected for the purpose of the maintenance of the assigned form and for the purpose of the adaptive compensation for the distortions of the wave front of the emission formed with telescope.In this article the original method of manufacturing of the lightened optical elements was proposed. It was shown on the basis of calculations and experimental data that the errors in the production of optical elements were found within the permissible limits.An example of the procedure of the production of the lightened mirror was given.

Method of determination of the storage capacity of visual, photographic and TV - images in the telescope, considering the influence of different distorting factors (physical, technological, instrument) was proposed. It was shown that the presence of the distorting factors (factor) led to considerable reduction in contrast of images and, as a result, to reduction in resolution, decrease in brightness gradations and drop in the storage capacity of fixing images, by the example of atmospheric turbulenceFormulas, which allow to determine the storage capacity of the image of telescope under the assumed operating conditions were proposed. It’s possible when the values of the diameter of the telescope’s main mirror (variable value) and angular dimensions of the real image of object (constant value) are known.Calculations showed that increase in the diameter of main mirror with given angular value of the image’s circle of smearing led to reduction in the storage capacity of image under the actual practice. Therefore with the study of the problem on the creation of telescopes with the increased diameter of main mirror it is necessary to simultaneously solve the problem of an improvement in the quality of image both due to the minimization of the influence of the distorting factors of telescope itself and by the means of the adaptive correction of this influence.Proposed method allows to determine the maximum permissible dimensions of the main mirror of telescope and, correspondingly, the possible price of entire work on creation and installation of telescope. It’s only possible when the specific value of storage capacity and the angular dimensions of the image of point are known.Method is applicable for both classical and adaptive telescopes.

The authors consider capabilities of manufacturing diffraction and hologram optical elements (DOE and HOE) with the use of the “Caroline 15 PE” machine. The purpose of the work was to increase the quality of binary DOE-HOE which is defined mainly by depth of the regular profile on the functional surface. It is shown that the maximum of this depth corresponds to the maximum of the etching selectivity of glass concerning a mask material. It is established that at thickness of chromic mask of 100 nanometers the PE method reaches depth of surface to 1,4 microns. It allows to increase the diffraction efficiency of DOE-HOE. Relative intensity of light in the second order of diffraction is 30 %; it allows to create new products of micro-optics.

With the framework of multi-liquid hydrodynamic approximation, the author proposes a computational model of non-equilibrium space-inhomogeneous plasma of discharge in metallic vapor in the compound with inert gas which has different temperatures of light and heavy particles. All  the functions of energy and state particle distribution were considered to be non-equilibrium and calculated in the course of evaluation. Beside collision processes in the kinetics of energy level population of plasma-generating components, radiative excitation by resonant lines expanded with different mechanisms is taken into account. Theory and experimental data are in good agreement (5-15%) with temperature fields and electron and heavy plasma particle concentration, and also with basic radiative and electro-physical characteristics of discharges in the mercury vapor with argon buffer.

The authors propose a realistic non-stationary mathematical model of gas-discharge emitting sources with periodical pulse, considering transfer of radiation of complex discrete-continuous composition in plasma and coat stabilizing the charge. System for information fitting of computing experiments was developed. Appropriate software was created. The authors compared the obtained data with the results of the experiment; the comparison proved applicability of the developed software and computer tools for investigation of systems and technologies using infrared, ultraviolet and visible radiating of powerful discharge lamps with wide nomenclature of gas and metallo-gas plasma-generating media.

The method of introduction of ferroelectric nanoparticles into artificial opals' pores was proposed and implemented. The optical properties of the original sample and the ferroelectric-doped crystal were compared. The theory that can describe and predict the spectrum’s observed features was developed. The electro-optical properties of composites were analyzed. The possibility of the nanosystem's secondary emission spectrum control was discussed.

Methods of conducting an experiment to investigate 3D Fizeau effect and processing its results were developed. Proposed processing method allowed us to increase S/N ratio up to approximately 10⁵. Developed method of conducting an experiment allowed us to carry out an experiment and process experimental data by series automatically.

The author analyzed the process of optical soliton’s occurrence due to the balance between two competing physical processes; they are dispersion spreading of light pulse and phase self-modulation (PSM) which occurred due to the non-linearity of optical signal’s propagation medium (Kerr effect). The method of compensation of the optical signal’s chromatic dispersion in the fiber was proposed. Analytical expressions of mathematical expectation and dispersion of the repetition period of solitons and the value of the solution signal were obtained from random time of the pulse’s arrival to detector. The obtained data must be taken into consideration when calculating signal-to-noise ratio in soliton of the fiber-optic transmission system (FOTS). The analytical expressions of time response, amplitude-frequency characteristics (AFC) and phase-frequency characteristics (PFC) were obtained for different input signals: for Dirac delta function and for Gaussian. These characteristics were conditioned by Rayleigh backscattering.

The physical phenomenon of "mechanoluminescence" was the subject of study conducted by groups of researchers from different countries. Despite the information about the processes in zinc sulfide and strontium and barium aluminates, the comparison of ways for their further use in the instrument was not carried out. This article was devoted to this comparison. There was a description of the process in the groups of mechanoluminescence compounds, marked above. Comparison of physical characteristics of processes was described in this article. Despite the similarity of the cause (mechanical action), that provides the glow the physical mechanism could vary greatly depending on the type of chemical compound. In the article the propositions about future research, aimed at finding the best ways of usage and applications of the mechanoluminescence, were made.

 It is of great interest to analyze the limit of specific resistance of disordered alloys both for massive models and for thin films and small particles in porous medium, and also to examine its influence on high-frequency conductivity. This work is dedicated to solution of these problems. All calculations are carried out for the model of metal as a model of Fermi gas of electrons o condition that the free path is equal to the average bond radius. The authors obtained formulas for static and dynamic conductivity of thin films and small particles in porous medium which can be applied both for nonmagnetic and magnetic alloys. The authors stated the field of applicability of the obtained formulas. They proposed and justified a hypothesis about reasons of the quantum limit existence for conductivity of alloys which is independent of magnetic order.