The dye doped jelly like gelatine is proposed as photosensitive medium of a new type. The medium allows to write down the stationary 3-dimensional gratings with high spatial resolution and may be used as an active medium for DFB-lasers as well as a material for reversible recording of holograms.
A possibility of light generation with super-Gaussian statistics using stimulated scattering of different types is theoretically predicted. It is shown for the first time that in the linear regime of SRS with broadband pumping the statistics of Stokes radiation is super-Gaussian with normalized dispersion higher than 100%.
The complex scientific program on investigation of optical irradiation influence on eye tissue is completed. The work includes: (i) studies of the fundamentals of the physical-chemical processes of light - tissue interaction in the eye, (ii) development of new methods for treatment of many eye illnesses (glaucoma, tumors of different etiology, including oncology), (iii) creation of practical instruments for clinical use in ophthalmology. (In collaboration with the Minsk State Medical Institute, Ophthalmology Laser Center, 3-rd Clinical Hospital, State Enterprises MTZ "Medservice" and "LEMT".)
It is proposed to use the diacetyle as an effective sensitizer for photodestruction of main ferments of a cell metabolism. It was shown that this substance is quite perspective for different medical applications including cancer phototherapy and selective photodestruction of the biological pollution in the environment.
The lasing in the blue region of the visible spectrum has been achieved in quantum wells heterostructures ZnMgSSe/ZnSSe/ZnSe under optical excitation at high temperatures (up to T=580 K). It was shown that the processes of recombination in a dense electron-hole plasma are responsible for the stimulated emission. High temperature operation of such laser is provided by low laser threshold owing to the high spatial optical and electron confinement. The results obtained will be used for elaboration of the vertical cavity lasers for the optical processing systems
The multidimensional method of g-spectrometry was proposed and theoretically proved. The method allows to increase the resolution of g-spectrometry by almost an order of magnitude.
The photoelectric characteristics and time responses of multilayer quantum sized structures of CdS/PETF with planar electrodes are studied. High light sensitivity of the structures under investigation is detected, and the possibility of wide-range variation of their main photoelectric parameters by structure's configuration variation is shown. The results obtained indicate the possibility for forming the wide-range sensitive photoresistors.
The small-angle iteration procedure is proposed to describe laser beam propagation in stochastic media with an arbitrary statistics. The results obtained can be used for adequate radiation description in atmosphere and biotissues.
A method for determination of the Mueller matrix of nondepolarized optical systems based on determining their independent elements is developed. The methods permits to reduce more than 2-fold an experimental data volume, and to increase an accuracy of determination of the Mueller matrix elements. The method gives new experimental possibilities for testing the physical parameters of optical objects.
Strict integro-differential equations describing leaky modes of anisotropic waveguides are formulated. The equations are reduced to a system of linear algebraic equations in respect to field values of a local area which allows the numerical study to be made.
On a basis of the developed formalism of commutative hypercomplex numbers with generalized inversion a new class of exactly solvable singular systems of the Fedorov equations are obtained.
Properties have been studied of the reversible recording of optical information on oriented liquid-crystal (LC) layers of nematic mixtures of azobenzene homologues which is based on isothermal phase transition or re-alignment of the layers as a result of forward and bañkward cis-trans- phototransformations of LC molecules under the action of the Ar-laser recording radiation (l=488 nm, P=7 mW). It is shown that the energy response and temporal characteristics of the information recording and erasure processes are substantially dependent on temperature and thickness of LÑ layer as well as on the composition of nematic mixture. (In cooperation with the Institute of General and Inorganic Chemistry of NASB and the University of Manchester, United Kingdom.)
The p-i-n-photodiodes have been developed based on InGaAsP/InGaAs/InP heterostructures for 1.3--1.55 mm wavelength and combined with optical receptacle connectors for fiber-optic communication links. The devices ensure attenuation up to 60 dB of the optical signal reflected into the fiber line and spectral sensitivity of 0.95±0.05 A/W at 1300 nm wavelength in the frequency range of 1.5--2.0 GHz.
Microsensors have been developed based on perforated super-thin substrates and micro-system technology. Prototypes of the devices with thin-film sensitive WO3 layer show an up to 1500-fold variation of the response characteristics with hydrogen concentration of 15,000 ppm. Narrow temperature region have been found where a microsensor with nickel oxide active layer is selectively sensitive to ethyl alcohol vapors. In other temperature regimes, the same devices show sensitivity to nitrogen compounds (ammonia, nitrogen oxides). Such micro-system microsensors make it possible to reduce power consumption up to a factor of 5 and increase their sensitivity by the same factor.
Phase transformations have been investigated that occur in refractory metal films under treatment with active arc-discharge plasma. Regularities have been established of formation of nitrides and carbides of refractory metals depending on the treatment conditions (temperature, duration, etc.). This method can be used in technological processes of microelectronics for formation of barrier layers.
Models have been developed for formation of optimal systems of informational support of experiments and tests of complex on-board redioelectronic systems. Based on the concepts and methods of Kolmogorov's theory for analysis of events and phenomena, a probability-statistical technology has been proposed for data processing by using procedures for the determination of functionally bound operations and subsystems and the intensity of information data flows in the subsystems. This makes it possible to optimize and enhance the effectiveness of the developed system software/hardware for organization of information processes and express evaluation of multi-channel data obtained in the course of testing on-board communication systems for electromagnetic compatibility.
Mathematical model and multilevel decomposition method for multicriteria optimization of transmissions with network structure as a whole is developed. They allow to determine optimal design parameters of transmission elements for the accepted criteria (deviation of the obtained speeds from the preassigned ones, the total transmission life and its mass), taking into account main functional, kinematic, strength and constructional restrictions. The obtained results are used for development of methods and software for automation of kinematic and strength computation of multiunit mechanical transmissions with complex structure.
A number of methods and effective algorithms of skeletization, filtration, extraction of informative features of handwritten symbols images based on the spectral models of symbols shape descriptors were developed which in comparison with known ones increase essentially a performance of image identification system keeping the same recognition accuracy. Both fast algorithms of descriptors calculation in various orthogonal bases and technique of these algorithms mapping onto parallel computing structures of systolic type were offered, which allow to synthesize signal processors and to raise their productivity.
Polynomial algorithms have been developed for the nonpreemptive two machine job-shop scheduling of fixed number of jobs with unbounded number of technological stages. It is shown that the same problems with allowed operation reemptions are binary NP-hard even for three jobs and any regular criterion. The pseudopolynomial algorithm is developed for preemptive job-shop scheduling of fixed number of jobs. These algorithms may be used in production scheduling and control systems.
The theoretical principles and methods to recognize dynamics of complex system on a basis of local-global parameters of state-space are developed. Proposed approach allows to come nearer to limiting opportunities of extraction of new additional diagnostic information hidden in dynamics of complex system state, to diagnose faster and more precisely presence of self-organizing process in investigated system, to control an optimality of parameter search managing self-organizing processes. Area of results application is an intellectual system creation of the analysis and modeling of self-organizing processes in complex physical, biological, ecological and technical system.
Theoretical foundations, methods and algorithms have been developed for automatic input and recognition of line-drawing images. It allowed to create systems for input and processing of map and engineering drawings that have the same parameters as the best world systems.
Necessary and sufficient conditions for the factorization of transfer operators at infinity for linear infinite-dimensional dynamical system are obtained. A method for the description of the structure for the infinite zeros of linear dynamical systems is developed.
The existence of a linear Pfaff system with two-dimensional time-variable and countable number of different characteristic sets of its solutions is proved.
Sufficient conditions of strong stability for two-layer operator-difference scheme are obtained. (In cooperation with the Institute of Mathematical Simulation of the Russian Academy of Sciences, Russia.)
The best regularity for distribution of real algebraic numbers of bounded degree has been proved. This has made possible to find the right transcendence measure for almost all real numbers and to generalize a famous theorem of Khintchine (1924). The generalization has never been proved before even for two-degree polynomials.
The characterization of the cone semispaces of partial convexity is obtained, and their number have been estimated. The algorithm of enumeration of the cone semispaces have been developed when the set of directions of partial convexity is finite. The problem of finding a partially convex hull associated with the cone semispaces is NP-hard.
A new parameter describing decay rate of the polarization of the electromagnetic field has been introduced in laser theory. It defines a complementary or alternative mechanism of nonlinear dynamics in a vector laser. It is shown that this new decay rate might drastically influence even dynamics of a class-A laser which exhibit full range of complex behavior including chaos. Full Feigenbaum scenario of transition to chaos has been found. Three types of crises in the chaotic attractor have been distinguished.
The predominance of the photochemical mechanism over the thermal one has been established in the initiation of laser-induced sputtering of aluminum by radiation of excimer XeCl-laser at near-threshold ablation fluences owing to resonant character of the incident radiation.
The atmospheric pressure glow discharge is obtained for the first time, the discharge's current voltage characteristic with rise of a current up to 15 A is increasing.
An interaction of photoexcited cationic porphyrins and metalloporphyrins with DNA components (nucleotides) is studied, when the latter being a part of artificial polynucleotides or natural DNA. It is shown that the charge-transfer interaction of the metal-free cationic porphyrin with one of the nucleotides, namely guanine, results in ~50% quenching of the porphyrin singlet excited state, but no such effect was observed for the metalloporphyrins. It is also shown that the mechanism and rate of the cationic porphyrin triplet state quenching by oxygen, when porphyrin is bound to polynucleotide, is determined by the porphyrin localization in the double helix.
To investigate vector correlations in photodissociation, an universal mathematical description of the photofragmentation dynamics is developed. The description is based on the universal formalism of orientation correlation functions. New models are proposed, that allow one to take into account peculiarities of the polyatomic molecule dissociation dynamics: the free recoil model, a model which is based on the assumption of the semiequilibrium photofragmentation, and also a model which enables one to consider both the inertial rotation of the parent molecule and the additional torque due to the rupture of chemical bonds.
The fast-diffusing oxygen quasi-molecule (dimer) in silicon monocrystals has been discovered by means of low-temperature infrared spectroscopy. The vibrational spectrum and binding energy of these complexes are determined. Their formation rate is found to increase significantly under fast electron irradiation of Si crystals.
The effect of giant magnetic resistance has been discovered for the first time in orthocobaltites with the perovskite structure doped with barium ions.
The technique for producing high-quality nonlinear optic crystals of argentum selenogalate (AgGaSe2) for use in laser communication and location systems in infrared range has been developed.
The modified system of the Bloch--Maxwell equations for describing the phenomenon of optical bistability in resonance fluctuating crystal medium with the "memory" of relaxation has been derived. It is shown that an increase in intensity and time of correlation of fluctuation disturbances reduces the cooperative branch of bistability curve, that indicates the possibility of guiding effectively the light flux in optical-bistable devices via the external source of color noise.
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The equation is derived that describes the dynamics of screening of the spatial charge field in semiconductors by photocarriers excited by an ultrafast laser pulse. The above equation enables to analyze in the same manner both collision-free and drift-diffusion modes of screening. In a collision-free approximation the spatial charge field is shown to decrease in time while oscillating with a frequency determined by non-equilibrium plasma frequency. This oscillating field behavior should reveal itself in such effects as generation of the second harmonic in reflected beam and generation of IR-pulse by a photoexcited surface of semiconductor.
The phenomenon of light focusing and defocusing in conditions of non-resonant Bragg scattering in periodically non-uniform media is investigated. Focusing conditions are found for forward and backward scattering, and focal lengths and angular apertures are determined for both focusing and scattering diffraction lenses. The possibility is shown to change the parameters of lenses by means of angular scanning of input light beam as well as by changing the modulation depth of diffraction grating. The important advantage of diffraction lenses is the property of transverse spatial invariance which consists in the invariability of focusing conditions for light beams when diffraction lens is shifted in a direction perpendicular to the beam's axis. It allows to effectively use such lenses for realization of optical interconnections in systems of multichannel optical information processing and communications.
The polarization dynamics is described of soliton in the Manakov system perturbed by joint effect of linear pumping and nonlinear (cubic) damping. A stationary mode of soliton's propagation in such system is found and it is shown that the only fixed soliton amplitude is determined by the ratio of pumping and damping powers and that amendments to the soliton's shape due to these perturbations partially compensate each other.
Source: "Main Results of Fundamental Research. 1996--1997". Eds. F.A.Lakhvich and N.N.Kostyukovich. National Academy of Sciences of Belarus, Minsk, 1998.
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