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[en] Peculiarities of the photorefractive effect (PRE) in undoped LiNbO₃ crystals were investigated. Measurement of change of birefringence at radiation propagation along the crystallographical axis x was conducted by means of the polarization-optical method. It is shown that all the PRE peculiarities in the investigated crystals can be explained in the model of the photovoltaic effect (PE). Population of small traps will take place under light exposure of the crystal, and then due to their photionization PE current resulting in change of birefringence in the illuminated zone, i.e. in PRE

[en] The results of investigation of level supersonic signal indicators with continuous and impulse radiator excitation in N₂O₄ medium in the range of temperatures from +20 up to +150 deg C and pressure 0-10 MPa are presented. It has been proved experimentally that the signal indicators with radiator impulse excitation show the best performance for these conditions. They can be widely used for provision of the normal operation of large-scale experimental stands and plants with gas-liquid cycle using nitrogen tetroxide as a coolant and working medium

[en] Specially developed level indicator is suggested with differential to-transformer converter of the float motion, operating in line with a movable electronic block, intended for indicating the level of the dissociating nitrogen tetroxide liquid phase. On the basis of the indicator elements the device is realized to measure the time of calibrated volume fillino. in by liquid nitrogen tetroxide in steady state operation of the experimental bench-marks

[en] The method to calculate the combination scattering power of the components of the dissociating N₂O₄ ↔ 2NO₂ → 2NO+O₂ gas subjected to the laser radiation effect is given. The combination scattering power has been calculated for temperatures 400-600 K, pressures 1-3 MPa, with the neodymium laser (λ=1.06 μm) as a source and the possibility of measuring the local temperatures and concentration of the given gas components with the help of the combination scattering has been analysed. It follows from the calculated data that combination scattering power of N₂O₄ ↔ 2NO₂ ↔ 2NO+O₂ gas in excitation with the neodymium laser as a source is sufficient for detection. Gas temperature is likely to be measured with the minimum error relative to stokes and anti-stokes bands of the combination scattering, produced by nitrogen tetroxide. From calculated data it also follows that measurement of NO₂ concentration in the range 400-600 K is possible. At the same time combination scattering power, produced by NO and O₂ components is sufficient for measurement merely with the concentration of the components of the order of 10¹⁸ molecules/cm³ guaranteed in static conditions only at N₂O₄ ↔ 2NO₂ ↔ 2NO+O₂ gas temperature 500 K and higher

[en] Laser radiation effect on absorption increase for 1.06 μm wave length was investigated in lithium niobate crystals. Photo-induced absorption phenomenon is explained by occurrence of some impurity centers or centers connected with intrinsic defects in a crystal energy gap as well as by their overcharging under illumination

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[en] The present paper describes the operation of an optical quantum oscillator (OQO) (laser), the active elements of which are made of an yttrium-aluminium garnet doped with the Nd³⁺ ions, being excited by the emission from pulsed injection semiconductor quantum oscillators (SQO) at the wavelength of 0.81 and 0.88 μ. The laser is pumped through the end face plane of the active element. At room temperature, the generation threshold for crystals 1 by 20 mm and 2 by 20 mm in size is 1x10^-4 and 3.7x10^-4j, respectively. In these experiments, a generation value twice as high as that of threshold generation has been obtained. The generation of Nd³⁺ ions has a character of a spike, whose duration does not exceed 1 mcsec. The generation power at the spike has been as high as 100 MW. It has been noticed that a change in the feeding conditions of the semiconductor lasers results in a change of the mean temperature of the diodes and their spectral chatacteristics and, accordingly, in a change of pumping absorption in the active element. In order to achieve the greatest absorption for each specific case of feeding conditions, the working temperature should be carefully selected. The dependence of the spectral characteristics of the injection laser on its temperature manifests itself markedly in pumping at the wavelength of 0.88 μ. When pumping to the wider and more intensive band of 0.81 μ, the above-mentioned phenomena are much less pronounced