Interband photorefractive gratings can be generated by illumination of an electro-optic crystal in the high absorption spectral region. In contrast to conventional photorefractive effects that rely on mid-gap doping levels, the gratings induced by such interband phototransitions exhibit a much faster response time (approximately equals 10 microsecond(s) at 1 W/cm² in KnbO₃) and are very robust with respect to intense illumination at sub-bandgap wavelengths. Due to the large light absorption, the interband gratings are limited to a relatively thin layer (typically 100-200 micrometers ) at the crystal surface. We discuss the main differences existing between conventional and interband photorefractive gratings. Besides by the electro-optic coefficients and the effective carrier mobilities, the strength of the gratings in a given crystal is controlled by the light intensity and the laser wavelength. Unlike in the conventional case, the photoconductivity and response speed depend here on the square-root of the light intensity. Interband photorefractive effects are interesting for applications of an optical incoherent-to-coherent converter and of an optical Joint Fourier Transform correlators based on interband dynamic holography. Finally we describe the use of this effect for creating robust and fast reconfigurable light induced waveguides in KnbO₃.

A novel approach for precise interferometric measurements of small transient phase shift of any speckled wave is discussed. The technique is based on a recently discovered polarization self-modulation effect in photorefractive crystals. The essence of this effect is that any intensity pattern is recorded in the form of the space-charge field inside the crystal. Then the same pattern propagates in the self-induced spatially-non-uniform electric field. As a result, the polarization state of the transmitted pattern becomes spatially modulated. Any pattern displacement results in change of the transmitted polarization distribution due to the linear electrooptic effect. Polarization modulation is readily converted into amplitude modulation by installation of a polarization analyzer after the crystal. In the proposed method, the crystal operates as a self-induced electrooptic modulator. The model of the polarization self-modulation effect is presented. It is shown that the signal-to-noise ratio of the proposed technique approaches to that of the ideal homodyne interferometer. Comparison of the proposed method with two- wave mixing technique is given.

We report the results of the analysis of the elastic field structure and the changes in optical permittivity tensor at optical frequencies in the region near the Z-plane of the BaTiO₃ crystal. The assumption of given interference light pattern with a fringe spacing (Lambda) and an independent on z modulation index m at steady-state is used. The photorefractive grating vector K lies in the plane passing through Z-axis of the crystal and making an angle of (theta) with the X-axis. Taking crystal surface to be traction free we consider two cases: (a) dielectric boundary and (b) short-circuited boundary.

The experimental investigation of the diffusion mechanism of photorefractive recording in BSO and BTO crystals at 633 nm under the conditions of sample pre-illumination by incoherent yellow-green light has been carried out. The nonmonotonic time behavior of diffraction efficiency manifesting itself as a local minimum has been found. Nothing of the kind is observed without preliminary illumination. The obtained results support the model in which the nonmonotonic evolution of a recorded grating is associated with the conditions of non-steady state and nonlinear photoconductivity in preexposed samples.

The external electric field influence on the stationary state, that existed in the photorefractive crystal under inhomogeneous illumination before the field appeared, is analyzed. IN this case, the additional charge grating is built-up and its amplitude is found to be proportional to the charge amplitude of initial grating and the field value. The building-up time of this grating does not depend on the field value and it is equal to the Maxwell relaxation time. However, the charge growth velocity is proportional to the electric field value. Consequently, the time interval which is necessary to obtain the set charge value providing sufficient diffractional efficiency decreases whereas the electric field increases. The expression connecting this interval with a corresponding value of the field is found. The dependence of a free charge carrier concentration on the light intensity for the two possible crystal types, in one of which the photorefractive centers are traps and in the other they are donors, is analyzed too. The conditions are elucidated where this dependence becomes sublinear for relatively not high levels of light intensity.

The equation describing the charge grating decay in the photorefractive crystals is obtained, and its solution is found as well. It is shown that the equation includes the dependence on the Maxwell relaxation time, the recombination time, the crystal temperature, the grating period, the donor and the acceptor concentrations. It is found out that the exponential charge decay in a usual sense takes place only after the lapse of time equal to the recombination time but not throughout the process. This is the principal difference of the charge grating decay from Maxwell relaxation of a single charge. The beginning of the charge grating decay process is described by Gaussian function. This function describes practically the whole decay process for large values of the recombination time. For small values of the recombination time the equation solution gives the usual exponential decay ofthe charge grating.

The rigorous solution in the plane-wave approximation of the light reflection boundary problem for the interface the isotropic medium - photorefractive crystal with the drift- diffusion nonlinearity mechanism is given. The possibility of the realization of the hysteresis light reflection phenomenon in this case under certain conditions is shown. The analytical expressions describing hysteresis behavior of the reflectivity as a function of the angle of incidence or that of the external electric field strength applied to the crystal are derived. By changing the value and sign of the applied electric field it is possible to transfer system from the total reflection state to the transmission state and vice versa. The obtained results are attractive for the elaboration of the possible devices for laser radiation control and optical information processing.

We propose an experimental method for the determination of the electro-optic coefficients of photorefractive crystals. Using anisotropic properties of the crystal and using the response of the crystal to different polarization states of the incident light, it is possible to determine the ratio between various electro-optic coefficients by measuring the gain in a two wave mixing set-up. The accuracy of the measurements is estimated and the obtained electro-optic coefficients for a Ba_0.77Ca_0.23TiO₃ crystal show good agreement with corresponding values already known from the literature.

Holographic recording properties and mechanisms are analyzed and compared in dielectric electrooptic crystals (EOC), dielectric colored alkali halide crystals (AHC) and amorphous semiconductor films (ASF) basing on author's investigations as well as on the literature data. Holographic photosensitivity parameters are introduced enabling the characterization of the recording mechanism efficiency independently of the particular optical and geometrical sample parameters, and allowing also for recording optimization. Ultimate specific recording energies for EOC, AHC and ASF are theoretically estimated. It is concluded that the ultimate recording energy for both crystalline and amorphous materials is of order of about 10^-6(cm²%). Now the best holographic parameters for the scalar hologram recording are achieved in EOC. Then come ASF and AHC. Yet AHC so far are superior at vector hologram recording. Finally, the conclusion is made that ASF can become serious rivals of EOC in holography and optical information processing if other material properties are taken into account such as hologram lifetime, sample size and cost, hologram self-enhancement possibilities.

The absorption, circular dichroism and photoinduced absorption spectra of Mn, P-doped Bi₁₂SiO₂₀ single crystal are studied. It is shown that dominant oxidation degree of manganese in this crystal is +4. The assignment of bands observed in studied spectra to electronic and vibronic transitions is proposed.

Optical absorption, power rotary and circular dichroism of crystals of the sillenite family Bi₁₂M_xI₂₀(M- elements I-VIII of groups or their combination) were measured. The t₁-2e charge transfer transition of the [VO₄]^3- tetrahedral complexes is found to make a negative contribution to the optical rotation of the vanadium sillenite. We present a model, which takes into account a negative contribution from the charge-transfer transitions of [MO₄]^n- complexes to the optical rotation in Bi₁₂M_xO₂₀ crystals. It was found that M vacancies and crystal field transitions of 3d- elements contribute significantly to the circular dichroism of sillenite crystals.

The copper exchange effects in waveguides containing different H_xLi_1-xNbO₃ phases are investigated. We have used x-ray diffraction, m-line spectroscopy in the visible, near UV and IR regions and holographic characterization methods. The crucial dependence of holographic sensitivity on phase composition has been found to be the specific feature of Cu:H:LiNbO₃ waveguides. It is established, that the main peculiarities of optical and photorefractive properties are caused by simultaneous formation of Cu⁺ defects and (OH^--Cu⁺) pair defects.

Bi₁₂TiO₂₀ single crystals were grown from the various melt compositions (5.0-10.0 mol.% TiO₂). The stoichiometric dependence of optical and photoconductive properties of Bi₁₂TiO₂₀ crystals is studied. It was observed that the lattice constant value depends on TiO₂-concentration in the melt. The melt composition dependencies of absorption coefficient and circular dichroism value have linear character in spectral range 410- 500 nm. The bismuth-richer melt-grown crystals performed the higher values of absorption coefficient and intensities of the band in the circular dichroism spectrum. It is shown that photoconductivity is more sensitive characteristic to melt composition. The crystal grown from the bismuth- poorest melt exhibits the photoconductivity which is two order of magnitude higher, than in crystal grown from the bismuth-richer melt, over studied spectral range. The crystal grown from 9 mol.% TiO₂ melt composition performs the maximal values of photocurrent and photoinduced absorption. Based on these optical and electrical results, the nature of the local centers in Bi₁₂TiO₂₀ crystals is discussed.

The transient dynamics of the internal space charge field was observed in two-wave mixing experiments in BSO crystals carried out at the wavelength of 633 nm under the external ac electric field. The effects involve practically complete disappearance of the initially strong space-charge field during continuous illumination of a sample by an interference pattern and the retrieval of the significant part of the initial field after the signal beam is switched off. Moreover, the compensated grating can be retrieved even after homogeneous illumination of whole sample without applying external field during many hours. The observations are explained in the frames of the monopolar free-carriers- transport model using the idea of spatial modulation of a sample photoconductivity. The change of the photoconductivity is due to non-equilibrium population of deep traps participating in photoexcitation of free electrons. The model is in accordance with the data of photoconductivity measurements indicating to the transient behavior of the photocurrent in studied BSO samples at the wavelength of 633 nm.

A statistical approach for the derivation of the phase conjugation dynamics is presented. For the optical scheme of the Double Phase Conjugate Mirror (DPCM) using Bi₁₂TiO₂₀ (BTO) and Bi₁₂SiO₂₀(BSO) crystals, comparison of our experimental data with the model calculations is given.

On the base of the analytical solution of the couple differential equations system in the photorefractive piezocrystal with transmission holographic grating the optimization of the diffraction efficiency is conducted by choice of the crystal orientation and linear polarization of the reading light. It has been theoretically established, that for bi₁₂SiO₂₀ piezocrystal with thickness 10 mm at different values of external electric field E₀ the maximum diffraction efficiency (eta) ^M is reached for the following magnitudes of the (theta) and (Psi) respectively: without electric field (theta) =42 degree(s), (Psi) =35 degree(s), with electric field 5 kV/cm (theta) =51 degree(s), (Psi) =19 degree(s). Without taking into account the piezoelectric effect these orientation and polarization angles have the following values: without electric field (theta) =0 degree(s), (Psi) =107 degree(s), with electric field 5 kVcm (theta) =43 degree(s), (Psi) =31 degree(s). It is shown, that taking into account the piezoelectric effect increases the maximum diffraction efficiency (eta) ^M in 2.13 times at E₀; in 2.47 times at E₀=5 kV/cm; in 1.75 times at E₀=1- kV/cm; in 1.43 times at E₀=15 kV/cm.

The analytical dependencies of crystal thickness, for which the diffraction efficiency optimized on the polarization angle reaches the maximum values, on the orientation angle are derived. It is shown that optimum thickness of the crystal is inversely proportional to its specific rotation and plots of dependence of crystal optimum thickness on the orientation angle are set of an equidistant curves with period 180 degree(s) corresponding different local maxima. A distance between these curves is defined by the specific rotation of the crystal (alpha) . The optimum thickness for the first local maximum can not be less than (pi) /(2(alpha) ). The magnitudes of crystal thickness, optimal for the diffraction efficiency of the hologram and gain coincide for some intervals of the orientation angle (theta) between the gating vector and direction [001]. Analytical expression, permitting to determine the azimuths of polarization of a reading light, at which the diffraction efficiency will be optimized simultaneously on the polarization angle and the crystal thickness, is found.

In this work we give a retrospective analysis of the development of optical technologies in Belarus. In the post-war period a great scientific and technological potential has been built up in this sphere, highly skilled specialist have been trained and prestigious scientific and technical schools have appeared. Belarusian multiprofile optical industry is noticed to be capable of producing not only the materials and equipment for optical production but also optical goods of the highest level of complication. The characteristics of cosmic photoequipment, photogrammetric and cinetheodolite techniques, a variety of laser devices and optical goods for civic purposes are given as an example. The instances demonstrating the realization of unique optical projects are considered as well. High quality of Belarusian optical production makes it be much in demand in Russia, Japan, USA, Germany, France, China, Korea, Sweden, Spain, England, United Arab Emirates and other countries.

A factorization of the integro-differential tensor wave equations of optics of dispersive anisotropic media is carried out. In the first-order partial differential equations obtained the integral operators of light velocities are involved in the compact covariant form. They give general description of dynamics of polarized wave pulses for any propagation directions and initial polarization states.

Long-lived transient gratings excited by UV laser radiation in the absorption band of synthetic diamond crystals have been observed for the first time. Decay constants of the gratings depend on the crystal defects nature and lie in the range of 0.1-100 ms that is 10³-10⁴ larger than that of thermal gratings. They are observed as slow tails of the scans which describe the time evolution of the signal diffracted by the laser induced grating in the crystal. Electron-paramagnetic- resonance shows a correlation between the EPR signal and long-lived grating amplitude. The defects with unpaired electrons are mainly responsible for the gratings observed. Selectivity of the long-lived gratings to the wavelength of excitation is shown. The gratings reveal a strong sensitivity to the crystal temperature. For example, the grating lifetime decreases by several orders of magnitude when the crystal temperature increases from 20 degree(s)C to 200 degree(s)C. It proves the defect nature of the gratings observed. Light-induced grating approach appears to be a sensitive tool for the investigation of defects in diamond crystals including those that do not yield the luminescence.

The focus of this paper is the characterization of electro- optic properties of single crystal thin films of organic material NPP grown by the plate-guided method. Characterization was performed using the longitudinal a.c. modulation technique. Half-wave voltage V_(pi ), figure- of-merit F, and electro-optic coefficient r₆₃ were estimated to be 3.24 kV, 0.98x10^-10 m/V and 25.8x10^-12 m/V respectively. We found that crystalline z-axis is off the normal to the plane of the film at an angle of 7 degree(s). We also proposed a transverse version of a thin film electro-optic modulator with low driving voltage, which is based on a single-arm thin film waveguide interferometer.

The nonlinear dynamics of electron-photon system under breakdown electric fields taking into account the processes of an impact ionization, spontaneous and induced recombination of charge carriers under conditions corresponding to streamer discharge in semiconductors is analyzed. It is shown that in a given system the different autowave regimes and formation of spatially inhomogeneous dissipated structures (DS) as the self-organization elements are possible.

Peculiarities of the absorption saturation in doping superlattices with n-i-p-i crystal type structure are established. Calculations are performed in the k-selection rule model taking into account the screening of the electrostatic potential by current carriers and the density state tails.

The presence of impurities in the crystals has an important influence on their properties. A sensitive method of the impurity control in the crystals without their destruction is the investigation of their absorption spectra. In this work we have studied the LaF₃ tysonite crystals widely used as the laser matrices. The LaF₃ crystals were grown from the melt by Bridgman-Stockbarger method using the reagents with trade mark high pure and chemical pure. The crystal absorption spectra were recorded in the range of 200-300 nm and the obtained results have shown that the crystals grown from the high pure reagents had no absorption bands in the UV region and the crystals grown from the chemical pure reagents had well defined characteristic absorption bands at (lambda) = 205, 218, 235, 248 nm. Spectral experiments have confirmed the assumption that the UV-absorption bands in the latter crystal samples were caused by the presence of CeF₃ impurity in the chemical pure reagents. A technique was developed for evaluation of CeF₃ content in LaF₃ crystals and in chemical pure mixture of LaF₃ with the accuracy +/- 0.0005 mol.%.

Universal method, permitting to form multi-ring light beams with a required quantity of rings from the circularly polarized Gaussian light beam, is proposed. This method permits to increase or decrease by 1 the order of an input beam wavefront screw dislocation, if beam has it. The method was realized by means of the optical scheme containing a biaxial crystal. Using biaxial KTP and (alpha) -HIO₃ (iodic acid) crystals Bessel and multi-ring light beams with the first and the second order dislocations are obtained experimentally. The second harmonic generation by mono-, two- and four-ring light beams possessing WFSD₁ in a nonlinear KTP crystal is studied experimentally.

The peculiarities of propagation of space-limited light beams in a periodic structure formed by crystalline layers of an arbitrary symmetry have been considered. It has been shown, that phenomenon of non-lens focusing may exist even in superlattices made from layers with a high symmetry. The character of changes of the light beams diffraction by decreasing the crystalline layers symmetry until orthorombical one has been analyzed. The influence of mutual orientation of crystallographic axes of layers on the light radiation focusing has been established. The region of X₃ axes disorientation for components formed superlattice, for which focusing properties of layered periodic crystalline structures are constant, has been obtained. The optimal characteristics of focusing systems on the base of layered periodic crystalline structures have been found.

We have realized dark spatial photovoltaic solitons at wavelength of 632.8 nm in Fe and Cu - doped planar optical waveguides in lithium niobate. It has been shown that for lowest TE modes the photovoltaic nonlinearity only partly compensated the light diffraction effect at the experimental conditions used. The development time of corresponding light-induced photovoltaic lenses ranged from 0.1 s to 30 s depending on the waveguide sample. For the highest TE modes we observed the exact compensation of diffraction effects in the time scale of some minutes followed in some cases by the termination of dark solitons formed because of the light overdefocusing.

The analysis of types of waves (modes) in planar dielectric waveguides with uniaxial anisotropy is presented. Main attention is given to examination of mode's characteristics in the vicinity of multiple roots of the dispersion equation. Using the method based on the contour integration technique, the effects of instability of an averaged ellipse of mode polarization are described and conditions of their observation are established.

The exact numerical and approximate analytical methods for calculation of the characteristics of leaky modes of channel optical waveguides produced in lithium niobate crystal by proton exchange are presented. Dependencies of attenuation coefficients of leaky modes on the crystal cut and waveguide parameters are investigated. Possibilities of minimization of the attenuation coefficients are established.

Effect of a light leakage may be observed as in planar waveguides formed in optically anisotropic materials as in primary isotropic multi-layer waveguide structures. This effect results in the exponential decay of the light intensity within the waveguide, but on the other hand it may be used to connect light beams within a substrate with guided light to excite waveguide modes. The characteristics of a light leakage in configurations corresponding to proton-exchanged waveguides in LiNbO₃ are discussed.

A modification of model describing optical structures forming in nonlinear ring interferometer (NRI) containing liquid crystal having Kerr effect is suggested. Case of optical field which is turned through some angle in cross section plane of the laser beam (in feedback of the NRI) is investigated. It is found that both screw dislocation order of the wavefront entering on the NRI input and phase shift of the optical field in circuit of feedback of the NRI effects on optical forming process equally strong. A theoretical analysis and simulations show any new possibilities of NRI applications: the identification of spiral dislocation order of an optical vortex (by shape of optical structures self-organizating in cross section plan of laser beam in NRI); the compensation of the optical vortex effect on evolution and result of the optical forming in NRI; basis of an arithmetic-logical optical device realizing addition operation.

The present work is devoted to the order parameter S estimation in the comb-shaped liquid crystal polymer thin films. The plymer under study was placed in the electrooptical cell and its homeotropical orientation was realized by the action of electrical field between the electrodes. The polarization absorption spectra of the empty cell and the cell with polymer were investigated at different incidence angles of the light beam. The method of interferometric extremum envelopes was used for the processing of the quasiperiodical absorption spectra observed. This method gives the possibility to obtain the optical parameters of the cell electrodes and to re- establish the true polarization spectrum of the polymer film. The polymer order parameter S was calculated from the dichroic ratio for the polymer absorption band at revealed (lambda) = 405 nm. The refractive index dispersion data obtained for the substrates and the polymer from the independent measurements were used for this purpose. The effects of the local field on the order parameter value were also taken into account.

In the work the effect of orientational inhomogeneity of nematic liquid crystals (NLC) on characteristics of diffraction optical elements (DOE), based on the system relief grating-liquid crystal, was considered. The analytical solution for the NLC director and refractive index spatial distribution has been obtained and the diffraction efficiency of the system relief grating-liquid crystal has been calculated for different diffraction orders. As a result, it has been found that inhomogeneous orientation of NLC leads to considerable variation of the diffraction efficiency across the DOE area.

New type of Maxwell equations solutions for nonparaxial surface Bessel light beams is investigated. TH-polarized field on the boundary of two adjacent media and in slab waveguides is studied. Dispersion equations for surface waves are obtained and analyzed. The conditions for existence of surface Bessel beams are determined.

We propose a method of rotation of higher-order Bessel light beams based on controlling phase difference between the interfering Bessel beam and a super-Gaussian or annular beam coaxial with it. TO realize the optically-controlled rotation of light field, a phase modulator based on quadratic or cubic nonlinearities can be used.

Bessel light beam self-diffraction in heavily doped n-InP has been observed for the first. In the near field up to four diffraction orders have been registered. Preliminary numerical simulations demonstrate very high sensitivity of Bessel light beam self-diffraction pattern to the nature of nonlinearity.

In the present paper the new strict solutions of Maxwell equations and vector wave equation for different modes of an electromagnetic field of nondiffraction beams of a light are obtained. It is shown, that the set of solutions is multiparameter and consequently there is an arbitrariness in choice of main types of modes. The expressions for the polarization characteristics of different Te and TM modes of Bessel beams are obtained. The principle of reciprocity permitting to realize transition from E-modes to M-modes and backward is justified. Their average density of energy and Poynting's vector have been calculated. The main legitimacies of TE and TM modes are established. The obtained results may be used in the description of the transformation of Bessel light beams of different types.

Bessel light beams in natural gyrotropic media are investigated. The components of electromagnetic field vector for a common case of vectorial Bessel beams of arbitrary order are obtained. The reflection and refraction of Bessel beams on the boundary of gyrotropic and nongyrotropic media is investigated. The properties of influence of natural gyrotropie on reflection and refraction coefficients and polarization of the reflected beams are analyzed and compared with the influence of the magnetic gyrotropie. Transformation of polarization states of the refracted field is studied.

In this paper properties of the generation of difference frequency of Bessel light beams at the quasi-synchronous interaction in periodically poled nonlinear crystals are investigated. The angular width of the synchronism for collinear and vectorial interactions under condition of first-order quasi-synchronism is defined. It is shown that in periodically poled nonlinear KTP crystals where the maximum nonlinear coefficient (sigma) ₃₃ is used, an effective generation of difference frequency of Bessel light beams takes place, which is in contrast with homogeneous media.

The problem of opposite interaction of longitudinal acoustic waves in dissipative media was considered, for instance, for plan parallel isotropic plate and one-dimensional periodic structure. All results were obtained for the normally incident waves. The boundary conditions of continuity were used to take into account repeated reflection. The questions of energy conservation were paid attention to in order to consider correctly the possibility of energy loss diminishing. The positive test result corroborated our method to be right. The analyses of dependence carrying through the investigated dissipative medium flux for different pressure amplitude ratio and phase difference were carried out. The numerical analysis allowed to propose the use of the opposite waves interaction for the control by energy flux passing through the dissipative media by means of changing of opposite source intensity and phase difference between interacting waves. The result can also be applied to the qualitative control of periodic structures.

The diffraction of light by the phase gratings of holographic type recorded by means of piezoactive ultrasonic wave in the gyrotropic cubic photorefractive crystal is investigated. It is shown that significant increasing of the diffraction efficiency on the holographic gratings may be reached by the external electrical field under condition of longitudinal electrooptical effect. The intermediate regime under study is close to the Bragg regime of the diffraction of light by acoustophotorefractive holographic gratings.

Possibilities of application of the formalism of the Mueller matrix for calculation of design of prism phase-shifting devices based on total internal reflection are demonstrated.

On the base of solution of the characteristic equation and the problem of independent elements of Mueller matrix of any nondepolarizing optical system the theory of Mueller matrices is developed and a method of their experimental determination is proposed.

We have considered a stratified periodic structure, consisting of any quantity of elementary cells, placed in an external magnetic field. Using boundary conditions for waves in each layer, we have calculated a matrix, which connects an incident wave to transmitted and reflected waves. Through elements of this matrix the complex coefficients of transmission and reflection of waves for al layered structure were expressed. We have calculated the optimum parameters of the structure, consisting of layers of KDP and Eu-glass. We have obtained the dependences of intensity, ellipticity and angle of turn of a main axis of polarization ellipse of reflected and transmitted waves on quantity of cells, on frequency of light and on a magnetic field strength.

Paying attention to the possibility of making the covers with low reflection of electromagnetic waves we have analyzed the characteristics of the electromagnetic waves under the condition of transmission through the artificial anisotropic medium on the metallic layer. The boundary value problem for normal incidence of electromagnetic waves on stratified periodic structure we have solved in case of the following structure: air- artificial anisotropic medium - layer of metal - air. Amplitude and phase characteristics of reflected and transmitted waves were calculated depending on the parameters of an artificial anisotropic medium and metallic layer, and the complex influence of anisotropic and chiral properties was also investigated. We find the optimum features of the structure required for reducing the intensity of a reflected wave on the certain frequency, here we take into account the absorption of waves in the sample and metal. Aluminum is taken as a metallic substrate. The artificial material is dielectric with the metallic microspirals, inserted in it. The axes of spirals are oriented in the same direction. IN this case the medium is characterized by uniaxial tensors of permittivity and chirality. For the orientation of the axes of spirals in the same direction the Nylon threads can be used, on which the spirals are reeled up. Samples of similar media were recently obtained at Stellenbosch University in Southern Africa. Our calculations allow to predict the experimental results in case of deposition of similar covers on the metallic substrate.

The study of multilayer heterostructures is of great interest for the development of materials with new properties. This objective can be achieved by means of crystal combination, which have necessary characteristics. When the length of electromagnetic waves is over the superlattice period, dispersion of vibrations propagating in the heterostructures is insensitive to the phenomenon at the layer boundary and, therefore, superlattice may be considered as homogeneous crystalline medium which characterizes by the set of effective parameters. The expression, which helps to define the effective tensor of dielectric permeability of the multilayer medium disturbed by the electric field of low frequency, has been found. By this, we considered the superlattice formed by crystalline layers of arbitrary symmetry. The properties of multilayer heterostructure have been analyzed at different configurations of electrooptical interaction. The possibility of creating of heterostructures with higher electrooptical efficiency as compared with its forming crystal components has been theoretically approved. The conditions of realization of superlattices, which are insensitive to the value ofexternal electric field, on the basis ofelectrooptical crystals, have been found.

Changes in the molecular structure of polymethyl methacrylate caused by irradiation with laser pulses of different powers were investigated by x-ray diffractometry methods. An analysis of the position and half-width of a halo in x-ray diffractograms was made. Coherent scattering regions and the distributions of the modules of the interatomic vectors were determined. Action of laser radiation on this transparent dielectric induced molecular structure changes associated with an increase in the molecular order in the amorphous matrix and with the formation of clusters at certain specific laser radiation energies.

Laser processing of the diamond can be presented as the following model. After absorption of the first impulses by the diamond, with the power density enough for evaporation, a furrow with a thin graphite layer on the bottom is formed on the surface of the diamond. Energy absorption of the following impulses of laser radiation takes place in the graphite layer created. While constructing of the rated model it is taken into account that during diamond graphitisation hexagonal planes are always parallel to the crystallographic planes (1 1 1) of the diamond in dependence of on the coming laser radiation direction. So the given thermo-physical model of the system diamond- graphite under laser influence predicts the difference in diamond processing productivity at the different crystallographic directions. This result confirms authors experimental researches. Diamond half-finished products which are obtained after sawing up of diamond crystals were put under laser radiation influence and were placed parallel to the axis ofthe fourth level and diamond plates parallel to the axis of the third level. It was discovered that the depth of the furrows obtained is 1,2 times larger than in case when the axis of the laser radiation direction is parallel to the axis of the fourth level, that is consistent with the given thermo-physical model ofthe "diamond-graphite" system placed under laser influence.

The orthogonal representation of wave propagation in magnetic crystals of triclinic and monoclinic systems is developed and generalized for mangetoelectrics. It is shown that, after introduction of principal velocities inversed to principal refraction indexes, Maxwell equations determine reciprocal tensors of velocities and indexes which depend linearly on directions and are similar to an angular momentum tensor. In the general case, when the non- reciprocity phenomenon takes place the 2nd order characteristic equations are obtained for determination of phase velocities instead of the 4th order equation. The two-dimensional representation of wave propagation is considered, it is established, that if gyrotropy takes place the introduced tensors are unitary ones. The simple expressions for dependence of ray (group) velocities, which directly define phase velocities and polarization of waves, on principal velocities in nongyrotropic crystals are adduced. Their generalization on purely and naturally gyrotropic crystals is discussed.