The effect of two-pulse photon echoes at the complicated action on a two-level medium with large inhomogeneous broadening of supremely short and quasiresonant pulses is investigated. Two versions of the action sequence of both pulses are considered. It is shown that the temporal properties of the echo signal are depended largely on the action order of indicated pulses. The effect of suppression of the optical echoes in the both cases at the action on a medium of the supremely short zeroth 'area' pulse is predicted. The qualitative procedure of definition of the complicated echoes spatial properties has been proposed and applied. It is shown that in indicated cases the diagrams of the echo signal intensity direction are not so peaked as in the case of common light echo.

The decay of two-pulse nutational echo has been experimentally investigated in S equals 1/2 spin systems (E' centers in silica) at microwave frequency. We have found that damping is well described by single exponential decay function. When the time delay between the pulses increases the measured echo amplitude decreases with the decay rate of 1/T₁, as expected from a T₁-T₂ model (Bloch model), and does not depend on the Rabi frequency (chi) . But with increasing of the first pulse duration t₁ the measured decay rate depends on (chi) linearly. Theoretical calculations within the high-field Torrey approximation give linear dependence of the decay rate on (chi) with increasing of the duration t₁. The agreement between the theoretical and experimental results is only qualitative. We assume that the strong difference between the theoretical prediction and the observed (chi) -dependence of the decay is caused by the frequency noise of the microwave radiation.

It is shown theoretically that, when two-level atoms are nonresonantly excited by a double light pulse that is a superposition of two rectangular pulses of identical frequency but different amplitude, it is possible to form multiple nutational echo signals whose amplitude is determined by the relationships between the Rabi frequencies of the double pulse, the inhomogeneous line width, and the detuning from resonance. It is established that these signals result from null beats between polarization vibrations at variable frequencies and at the generalized Rabi frequency. The optimum conditions for observing multiple echo signals in different experimental situations are considered.

Applicability of the Bloch equations for describing decay of transient nutations in a two-level spin system with homogeneous line broadening is studied experimentally. The NMR nutation signals in glycerin were investigated for 10 less than or equal to (omega) ₁T₂ less than or equal to 150, where (omega) ₁ equals (gamma) B₁, with (gamma) the gyromagnetic ratio and B₁ the amplitude of the magnetic component of the radio-frequency field, and T₂ is the transverse relaxation time. It is found that in a high-power field ((omega) ₁T₂ very much greater than 1) the nutation decay rate is independent of (omega) ₁ and is quantitatively described by the Bloch model. The data is compared with the data on non-Bloch ((omega) ₁-dependent) EPR-nutation decay in quartz [R. Boscaino, F. M. Gelardi, and J. P. Korb, Phys. Rev. B 48, 7077 (1993)].

Particular features of cw-laser radiation resonant interaction with ions of collisionless plasma in homogeneous strong magnetic field (order of some Tesla) are investigated theoretically. It is found that the particle rotation movement changes dramatically the resonant interaction features and the properties of laser-induced fluorescence signal that was proved experimentally. The possibility of 'ion-cyclotron photon echo' observation from coherently excited ions in homogeneous strong magnetic field is discussed.

The polarizations of photon echoes and superradiance signals formed by incoherent partially polarized exciting pulses are calculated in case of arbitrary values of the resonant level angular momenta. It is shown that the temporal shape of incoherent photon echoes may reproduce the reversed temporal shape of the first exciting pulse.

Multiple photon echo generation process in extended crystals is investigated taking into account both the contribution of irreversible relaxation during whole excitation time and propagation effects caused by the resonant medium influence on the exciting pulse sequence and echo-responses.

The structure of software package for simulating processes of echo-responses generation in optically dense medium is investigated. Complete analysis of the mathematical model realizing multipulse long lived photon echo forming in resonant media is presented taking into account a non-linear evolution of radiation and an irreversible relaxation during the whole time of a pulse sequence action.

The formation of echo signals by the unhomogeneous pulses is discussed, when a destruction of a coherency caused by this inhomogeneities takes place. It is formulated the conditions for the restoring of this coherency.

The effect of heat ballistic phonon pulses of the nanosecond duration on the inverted photon echoes in ruby with the concentration of Cr³⁺ ions of 0.2 wt.% and 0.03 wt.% and in LaF₃:Pr³⁺ for 4777 A (³P₀ - ³H₄) transition with the concentration of Pr³⁺ ions of 1 wt.% at temperature 2 K is studied. The basic result of given work: observation of coherent interaction of noncoherent heat phonons with impurity (interaction without coherence loss).

The boundary conditions for Torrey equation are proposed, which describes the spin echo signals under condition of the spin diffusion. They are used for calculation of the spin echo intensities for some pulses sequences. The result coincided with the solution which was received by Torrey without using of any boundary condition.

In the present work, stimulated photon echo (SPE) is numerically simulated, on the base of the semiclassian theory. Splitting of the ground state is taken into account.

A theoretical description is given for such interesting properties of radiofrequency (rf) polarization echoes in piezoelectric powders as the existence of dynamic echoes and memory echoes, the integration effect when successive coherent pulse pairs are applied to the sample. These and other important properties of the echoes are explained from one and the same point of view by the use of nonlinear formation mechanisms based on the interaction of acoustic vibrations with the dislocations which are effective in the rf frequency domain. A phenomenological model is elaborated for dynamics of dislocations in mechanically vibrating piezoelectric particles resonantly excited by short duration pulses of rf electric field. The model includes both the reversible and irreversible moving groups of dislocations generated by Frank-Read sources. The amplitude-dependent dispersion and amplitude-dependent damping obtained by use of this model constitute two of the three nonlinear mechanisms responsible for the formation of the polarization echoes in piezoelectric powders with the signals naturally consisting of both the dynamic and the memory components. The third type of the nonlinearities, the field-mode interaction, consists of the electrostriction due to the irreversible motion of charged dislocations and the nonlinear electrostriction.

It is proposed that the lack of memory components in microwave polarization echoes in ZnO powders is a consequence of absence of mobile dislocations in the powder material used. We suggest a somewhat modified form of the nonlinear mechanism related to the lattice anharmonicity: amplitude dependent dispersion and damping. General expression for dynamic two pulse echoes is derived by use jointly all the three known types of nonlinear mechanisms inherent in pure elastic lattice. The numerical analysis of this expression as a function of the pulse amplitudes, the pulse widths and the pulse separation shows good agreement between the theory and the existing experiments in broad range of amplitudes and widths of the pulses. Several important material constants relevant to the nonlinear mechanisms in ZnO powder are estimated as fitting parameters.

A method of integrodifferential equations associated with the optical Bloch equations is used to consider the boundary-value problem of nonlinear reflection (refraction) of the laser beams on the superthin film doped by the two-level atoms. An allowance is made for the phase memory effects exhibited by two-level atoms in response to pulses of fields resolved in space and time. A generalized Lorentz-Lorenz formula is derived for a nonlinear complex refractive index of an doped film in the region of an absorption band when this index depends nonlinearly and nonstationarly on the field inside the film. We derived generalized synchronism conditions to investigate the angular distribution of reflected and refracted primary photon echo signals.

Time-delayed second harmonic generation has recently been reported in an atomic vapor of Cs at a temperature near 180 degrees Celsius and situated in a magnetic field of the order of a killogauss. Short 10 ps excitation laser pulses at 885 nm were used to excite a macroscopic electric quadrupole density which was then observed to radiate at 442 nm after a delay of a few hundred picoseconds. The experiment is complicated by the presence of several superfluorescence transitions some of which radiate close to the 442 nm wavelength. These emissions are also delayed and our strategy is to set the experimental conditions so that they only become appreciable after the second harmonic emission is complete. In this paper we show how the second harmonic develops by considering the evolution of the radiation pattern of an isolated atomic radiator (not forbidden to radiate at the second harmonic even in the absence of a magnetic field). We estimate the intensity of the superradiant second harmonic emission and obtain agreement with experiment. Excellent agreement is also obtained between measured and calculated delay.

It is shown that under specific conditions the two coherent pulses can be bounded in the two-component medium and propagate as a unified excitation. The specific features of formation and propagation of coupled pulses are discussed.

Superradiance in spin systems is studied theoretically on the basis of a microscopic model corresponding to nuclear magnets with dipole spin interactions. The onset of pure superradiance is shown to be caused by nonsecular spin interactions. While the effective interaction of spins through the common radiation field, as well as the resonator thermal-noise field, are not able to initiate coherent self-organization resulting in superradiance.

In three-level systems one can realize amplification of radiation without inversion by creating a coherent superposition of lower states. This concept applied to the superradiant emission may allow us to get inversionless superfluorescence. Such a possibility is demonstrated for (Lambda) -scheme of the operating transitions. We discuss the problem how to create the coherence of lower states and the effect of the lower level splitting on superfluorescence.

Estimations of the superradiant energy flux show that for crystalline densities of radiators this flux may be comparable with the atomic unit. This assures the highly nonlinear behavior necessary to observe a pulse of high harmonics during superradiant pulse. We estimate efficiency of the third harmonic production in the frame of two-level model.

The propagation of electromagnetic radiation pulses in a medium emulated by the two-level atoms is considered. Ground state is not degenerated, excited state is characterized by the angular moment j equals 1. The exact steady state solutions of the Maxwell - Bloch equations without slowly varying envelope and phases approximation were found, that are generalization of a known solutions by Bullough and Ahmad for the scalar case.

We propose a new type of accessible sources of ultrashort pulses based on the phenomenon of collective coherent recombination (superradiance) of electrons and holes in semiconductor heterostructures. We find and analyze a novel regime of an ultrafast operation of quantum-well or quantum- dot semiconductor lasers in which a quasiperiodic sequence of femtosecond superradiant pulses is emitted under quasi- stationary pumping. According to our calculations for AlGaAs- GaAs heterostructures, the coherent optical pulses of duration approximately greater than 30 fs and peak intensity approximately greater than 100 MW/cm² can be generated in a low-Q cavity of length approximately 10 - 30 micrometers. It is shown that the same process of femtosecond superradiant recombination can be used for the room-temperature generation of optical coherent emission in multiple quantum-well or quantum dot GeSi/Ge structures employing direct radiative transitions from the (Gamma) -valley.

Linear coupling of helical optical modes in twisted and birefringent inhomogeneous fibers is rigorously incorporated to the newly derived polarization transfer equations, and statistical polarization parameters of partially coherent light emitted by a broadband source and transmitted through a dispersive single-mode fiber with random inhomogeneities are calculated analytically in the limiting case of slow cross talk between helical modes.

The new wave equation describing nonlinear propagation in isotropic dielectric media of any polarization optical pulses containing only a few oscillations of light field has been obtained. The polarization self-action of such extremely short pulses is shown to be in change of orientation of their electrical field amplitude vector along the direction of propagation proportional to a square of a field amplitude and the rotate velocity of amplitude vector.

Boundary problem of quantum optics for spontaneous emission of atom embedded in one-dimensional chain of discrete dipoles is solved. The role of boundary effects caused by violation of translational symmetry in atomic spatial distribution is investigated. Life time of excited state and frequency shift of atomic transition are calculated. It is shown that these spectral characteristics significantly depend on atomic position in the chain. Angular distribution of spontaneous photons is also investigated. Theoretical analysis is based on the system of Heisenberg equations for atomic and field operators. For the calculation of the mode functions it is employed as the method of integro-differential equations.

Kinetics of superradiance for a system of two-level emitters interacting with the quantum electromagnetic field is studied. A closed set of equations for atomic correlation functions is obtained which takes into account new decoupling of three- particle correlators. These equations yield a better description of experimentally observed shape of superradiant peak than the standard theories.

At densities that are typical of condensed matter, a propagating electromagnetic field mediates interactions between polarizable constituents of a material in what is known as the local-field effect. Previous investigations of the local-field effect have been limited to a single polarizable component of a nonlinear material. For multicomponent media, we have found that the interaction of laser radiation with an optically nonlinear component of condensed matter is fundamentally altered by the presence of another polarizable component as a result of the local-field effect. Novel effects include local-field enhancement effects, local cooperative decays, and coherence transfer and coherence exchange processes.

The condition for a stimulated formation of a coherent Bose- condensate of the Bose-particles is studied. The recently published experimental observation of the Bose-condensate interference, and the idea of an 'atom laser' generating the coherent atomic states are discussed. The Gross-Pitaevsky equations are generalized, where the interaction of Bose- condensate with incoherent subsystems of the particles is taken into account.

Steady-state free induction decay (FID), hole burning (HB) and transient nutations (TN) decay are investigated in ensemble of two-level particles with inhomogeneously broadened spectrum. The influence of x- and y-noise components induced by the coherent field exciting the resonant transition is considered. It is shown that 'longitudinal' (x) and 'transverse' (y) noises give the contribution to both T₁ and T₂ relaxation processes. This effect accelerates TN decay and changes the saturation broadening seen in HB and FID. It is found that when field-noise contributions to 1/T₂ and 1/T₁ relaxation rates are dominant and equal to each other, the Bloch's saturation is changed to Redfield's saturation. Comparison with experimentally observed FID and TN in nearly ideal spin system (color centers in quartz and silica) is discussed.

The effect of phase-conjugate feedback on the semiconductor laser dynamics is considered theoretically. The optical feedback is realized on the base of the intracavity four-wave mixing in the Cs vapors.

The role of near field effect is investigated in the boundary value problem of nonlinear resonant optics at the interaction of steady quasiresonant optical radiation with the film of two-level atoms. Dynamical detuning from resonance, nonlinear index of refraction, reflected and refracted waves are analyzed on the basis of solution of closed system of integral field equation and optical Bloch equations with account for discrete-continuous distribution of two-level atoms. An essential dependence of near field effect upon type of symmetry of atomic distribution is shown.

We have theoretically investigated the process of spontaneous emission of initially excited two-level atom inside and outside of ultra-thin dielectric film. Dielectric medium is considered as discrete-continuous system of interacting dipoles. For the solution of this boundary problem of quantum optics we use Heisenberg equations for atomic operators. Mode functions of ultra-thin film are calculated by direct solution of integro-differential field equation. Coordinate dependences of excited state life time are analyzed and it is shown that consideration of near-field effect may essentially change spectral properties of the atoms located at small distances from the surface.

Generalization of Gibbs distribution over the quasienergy states of moving molecules is successfully used to describe the thermodynamic properties of antiferroelectric phase transition in an ideal (collisionless) gas of two-level molecules. According to the method, there appears a self- consistent stationary polarization wave which is well agreed with that predicted on the basis of straightforward solution of the optical Bloch kinetic equations. It is found that a novel phase of gaseous crystal of the antiferroelectric type will emerge as a result of weak first order phase transition. Basic thermodynamic properties of this antiferroelectric phase transition are outlined and some estimates for possible experiments in real gases are presented.

The excited state absorption (ESA) spectra in the UV active media LiCaAlF₆:Ce³⁺ single crystal was studied by the amplified spontaneous emission technique. The nature of the ESA spectra is discussed.

This report presents an investigation of the interaction between optical radiation and photoinduced electrons in photorefractive crystals. It was established that the laser beam incident with the domain structure of piezoferroelectric crystal can be generated not only second optical harmonics but also an acoustic waves at the first and second harmonics. The acoustic generation due to the optically excitation and the following redistribution of the free electrons in domains.

The coherent state representations of the group G equals W₁ (direct product) G₀ [where G₀ equals SU(2) or SU(1,1)] are used in computer simulations of the dynamic of single two- level atom [G₀ equals SU(2)] interacting with a quantized photon cavity mode [Jaynes-Cummings Model (JCM) without the rotating wave approximation] and, in general, nonlinear in photon variables. The second case [hyperbolic Jaynes - Cummings Model (HJCM), G₀ equals SU(1,1)] corresponds to the quantum dynamics of quadratic nonlinear coupled oscillators (the parametric resonance on double field frequency and a three-wave parametric processes of nonlinear optics). Quasiclassical dynamical equations for parameters of approximately factorizable coherent states for these models are derived and regimes of motion for 'atom' and field variables are analyzed.

This work is devoted to the description of the interaction between n-level atom and a large dissipative system (heat bath). SU(n)-group coherent states as useful and convenient basis are employed. Fokker-Planck-like equations for (rho) - symbol of reduced density matrix taking into account possible squeezed fluctuations of heat bath are derived. New formulas for correlators of the transition operators between levels of system are obtained and influence of squeezing on the shape of radiation lines is discussed.

The difficulties associated with surface divergences, of a consistent QED theory in describing of the natural broadening (NB) of atomic systems are studied. This problem seems to be clearly and sensitively (in experimental meaning) appeared in the case of heavy multicharged ions. To overcome this difficulty we have used a quantity of elementary interaction length, an analogy of the length of coherence. We have obtained that the NB contains a linear l-divergence besides of a logarithmic one arising in standard QED calculations. A Z- dependence has allowed us to suggest carrying out the experimental testing of QED in the highly ionized atoms with the aid of more accurate technologies.

In the case of multiply-charged ions when energy levels with the same values of the total angular momentum J, its projection J_z and parity P may overlap, the SD difficulties are shown to manifest themselves in QED calculations of the respective spectral line profiles (SLPs). In this case we have used the regularization method of cut momentum L. A logarithmic L-dependence seems to be contained in the obtained formulas of NB and SLP. On the example of hydrogen-like uranium U⁺⁹¹ the SLPs have been calculated which spectra are deformed. It has been studied a dependence of SLPs from cut off momentum L, state i> and mutual distance (Delta) E_ji.

The three known models of quantum optics concerned the resonant interaction of three-level atom with two modes of field ((Lambda) -, V- and (Xi) -atom) was demonstrated to have the one general solution. The diagonalization method of block matrices was used to calculate the evolution operator of the atom-field interaction Hamiltonian. The method is outlined in detail by the example of the (Lambda) -atom model.

Water-ion transmembrane transfer in maize roots under the effect of infrared laser radiation with power 2.4 mwatt was studied by NMR method. It is shown that laser radiation (LR) alters the dynamics of spin-spin relaxation and increases the rate of transmembrane water exchange and ion penetration which do not depend on the type of paramagnetic ions doped into the intercellular space. The radiation results in the increase of the effective self-diffusion coefficient of water, and it correlates with the data on the effect of LR on the velocity of cytoplasm movement. The data on the decrease of the resistance of Nernst layers in the summary membrane permeability due to 'blowing off' its outer parts by the intensive cytoplasm current are used to explain the obtained results.

In the given paper on a basis electron-phonon model in view of strong correlations the renormalization of conductivity electron mass is carried out. Its dependence on frequency of falling light and from parameters of electron-phonon interaction is determinated. The consent with available experimental data is marked.

The excitation of semiconductor microcavity modes (ZnSe films on Cr and Cu surfaces) were investigated by femtosecond pump- supercontinuum probe spectroscopy in wide spectral region 300 - 800 nm. Photoinduced red shift of cavity modes due to parametric pump of ZnSe film and film-metal interface and the generation of coherent phonon oscillations in ZnSe were observed.

Relaxation of fullerenes in solids and solutions was investigated by femtosecond pump-probe technique at various experimental setups. Intensity of excitation pulse was varied at 10¹⁰ - 10¹² W/cm², energies of pump and probe quanta were changed from 1.57 to 3.14 eV, pulse duration -- from 60 to 350 fs. An increase of absorption was observed in solutions with a time scale of 1.2 ps for C₆₀ and 0.15 ps for C₇₀ after excitation of HOMO-LUMO transition. It was attributed to symmetry breaking of excited molecules. Observed for solid C₆₀ dependence of relaxation rate on the density of excited molecules and on the wavelengths of the pump and probe pulses is explained by 'hot' singlet-singlet annihilation the rate of which is proportional to R^-3. Comparison of photoinduced absorption and bleaching decays allowed to conclude that only a small fracture of excited molecules produce localized charge carriers, mainly by excitonic annihilation proces and these carriers are responsible for long-lived residual absorption observed in photoinduced absorption kinetics. Difference absorption spectra observed near zero delay time were similar to electroabsorption ones superimposed on excited state absorption of C₆₀ film. This electroabsorption feature disappeared in phase with pumping pulse. This phenomenon is connected with Stark shift in strong electric field of the powerful pumping pulse.

Experimental data on long-lived stimulated photon echo and photochemical spectral hole burning which cannot be explained by means of stochastic spectral diffusion (SD) theory are discussed. They are explained with the help of the dynamical SD theory developed recently.

In this paper the results of experimental investigation of temperature dependence of two-pulse photon echo amplitude in a Y₂SiO₅:Pr³⁺ crystal are presented. The new dephasing mechanism, connected with thermal-activated transitions of Pr³⁺ ion between nonequivalent positions in the lattice site, is used to explain the peculiarities observed experimentally.

An experimental investigation was made of the optical absorption spectra corresponding to transitions in the Pr³⁺ ion in crystalline LaF₃ matrices. The investigation was carried out in the temperature range 5 divided by 80 K. An anomalous redistribution of the intensity was observed in the absorption spectrum of a Pr³⁺:LaF₃ crystal. This redistribution did not agree with the hypothesis of the Boltzman population of the states in discrete multilevel systems.

The contrast and steepness of spectral repers, detected by two nonlinear Doppler free techniques -- photon echo in standing waves (PESW) and saturated absorption spectroscopy (SAS) -- are investigated at 0 yields 1 (nu) ₃ P(33) A₂¹ SF₆ transition for identical experimental conditions (over gas pressure and exciting beams geometry) versus intensity of CO₂ laser radiation. S/N advantage of PESW technique as compared to SAS method is demonstrated. The increasing role of slow molecules in generation of photon echo response at elevated time delays between exciting pulses manifests itself experimentally in slowing down the photon echo decay rate.

The method of a stimulated photon echo with specially selected linear polarizations of pumping pulses of a coherent resonant radiation is applied to a research of depolarizing collisions in molecular gas SF₆ and its mixtures with buffer gases He and Xe. For the first time in one experiment the rates of a collisional decay of three lowest moments of polarization (population, orientation and alignment) are defined in an ensemble of gas particles. These rates of a relaxation are measured as functions on longitudinal velocities of resonant particles. In the frames of an experimental accuracy any noticeable dependence on velocities of particles was not detected both for orientation and alignment neither in pure resonant gas SF₆ nor in mixtures. This result confirms the standard theoretical approach to depolarizing collisions. In pure SF₆ decay rates of orientation and alignment have proved lesser than relaxation rate constant due to velocity changing (elastic) collisions. It means, that only the part of elastic collisions participates in destruction of multipole polarization moments of resonant levels. In comparison with our previous work the evidence is obtained that the relaxation of multipole moments seems to be j-dependent one in a medium of molecular gas SF₆.

Kinetics of the decay of transient gratings (four-wave non- simultaneous interaction) in nitrobenzene liquid in the femtosecond time scale is studied. Experimental results are explained in terms of coherent vibrational molecular motion in liquid. A strong dependence of the kinetics of the signal decay on the polarization of the probe field is discovered. The beats of underdamped vibrational modes of nitrobenzene are separated.

The regularities of the two-pulse photon echo generation in doped crystals under changes of the angle (alpha) between directions of propagation of pumping pulses are investigated theoretically. The explanation of some experimental regularities, in part, the modulation character of the response intensity dependence on the angle (alpha) is presented. The angular spectroscopy possibility is discussed.

Saturation spectroscopy in inhomogeneously broadened media with excitation dependent dephasing is considered. We calculate probe beam absorption. As pump and probe fields are applied simultaneously, there is coherent contribution in probe field adsorption coefficient. It is displayed in box- like 'coherent' hole sitting on the smooth population- difference-hole seen by the probe field. We consider two models of polarization dephasing. First is based on modified Bloch equations (MBE) taking into account dephasing suppression by strong excitation. The second is developed on the base of non-Markovian perturbation theory (NMPT). We found the great disagreement between the results of these two models. Solution of MBE gives about 15% depth of the box-like hole relative to the maximum deviation of the probe absorption coefficient, whereas NMPT predicts 100%. This difference originates from Lorentzian approximation taken in MBE derivation. The last gives incorrect description of the wings of the homogeneous absorption line.

The modulation of magnetic field in paramagnetic resonance caused the amplitude and phase variations of the spin-system response at modulation frequency, depending on relation between modulation period and relaxation times of the magnetic system. The scanning of magnetic field or modulation frequency allows to expose 'relaxation structure' of the system, caused, for instance, by space distribution irregularity of the paramagnetic centers.

The techniques which allow the stimulated photon echo to be used for digital addition are proposed. Time encoding is used to represent the input multibit numbers by laser pulse sequences. The on- and off-bits are encoded by the pulse intensities. The implementation of the logical operations AND, OR, XOR, and EQV is fulfilled in one setup. The setup includes an interferometer of the Mach-Zehnder type. To process the different bits in parallel a technique of frequency scanning within specimen inhomogeneous linewidth is invoked. Various adders are considered. An operation of both the half adder and full adder devices is based on cyclic repetition of the procedures SUM and CARRY. A carry-free adder with time data encoding based on the residue arithmetic is also considered.

The method of information locking under photon echo regime have been suggested. To lock a data written in a resonant system the subjection of a sample to external inhomogeneous electric field may be used. The change in gradient of that field between writing and reading of information causes change of frequency distribution of optical centers over inhomogeneously broadened line resulting in the photon echo generation damping. The prospects for the method use are considered.

Coherent amplification, deformation and shortening of ultrashort pulses are considered in the case of a highly doped fiber with dominant inhomogeneous broadening of a spectral line. A promising possibility of parallel multichannel processing of complicated optical signals separated in time and/or in frequency is demonstrated.

Kinetics of spatial-frequency gratings decay determined by inter-atomic interactions of the two-level medium in solids is theoretically investigated. Building of the theory is oriented towards search for such optical experiments in which kinetics of the SFI-gratings could be studied in a simpler way. Analytical solutions for instantaneous diffraction signal and signal of the stimulated photon echo are obtained.

Inherent possibilities of digital processing of broadband signals and images envisaging further development are considered. The greatest problems in this regard arise when we attempt to perform such integrated transformations as Fourier convolution and transformation, requiring a great many of operations of multiplication and addition. While amplification of velocity of switching of the basic elements has a theoretical limit, the degree of paralleling of multiprocessor systems is limited by the complexity of control devices. One of the ways of essential amplification of the processing systems' speed consists in execution of integrated transformations via specialized analog processors, which become a constituent of the common multiprocessor system. The role of such analog devices can be taken by echo-processors, among which the photon echo-processor (PEP) exceeds its analogs by many basic parameters. The latter has an important advantage, i.e. an ability to process both one-dimensional signals, and fields and images within one step of its work.

Neutron scattering from ultrasonic waves in silicon and KBr single crystals was studied. By the use of neutron spin echo spectroscopy we have observed ultrasonic phonons for the first time by inelastic neutron scattering. One, double and zero phonon scattering were observed in Si. The intensity of the last scattering was almost independent from the acoustic wave amplitude. These results are in a good agreement with dynamic theory calculations. The results obtained in KBr are consistent with a model that each mosaic bloc oscillates as a whole. Our approach lends itself for the investigation of ultrasonic waves in wide varieties of substances.

Total external reflection effect improves the depth sensitivity of Mossbauer spectroscopy up to 1 - 5 nm. At grazing angles of incidence of collimated radiation from radioactive source on resonant film it is possible to measure simultaneously the intensity of the specularly reflected wave and the secondary radiation emission (e.g. conversion electrons) as a function of energy shift (Mossbauer spectra). Variations of grazing angle in vicinity of the critical one of total external reflection (1 - 6 mrad) allow to determine the hyperfine interactions distribution over depth in resonant film. We present the results of such investigation for ⁵⁷Fe/Sc/⁵⁷Fe and oxidized ⁵⁷Fe films and briefly describe the main problems appearing in the course of interpretation of Mossbauer spectra in this geometry. The usage of pulsed synchrotron radiation instead of the radioactive sources has essential advantages: (1) it has quite good natural collimation (approximately 10 (mu) rad) and (2) it opens a new way for nuclear resonant scattering investigation -- in time scale. The example of interpretation of time spectra of resonantly reflected beam from oxidized ⁵⁷Fe film is done.

A possibility of amplification without population inversion at gamma-ray transition due to excitation of nuclear coherence via coherent optical driving of the electron coupled with nucleus is demonstrated. Hyperfine splitting and isomer shift allow us to get inversionless amplification at gamma-ray transition via nuclear coherence created by the optical driving field.

Quasienergy spin states representation as a method of describing the influence of nuclear spin coherent dynamics on Mossbauer gamma radiation parameters is considered. The conditions of inducing coherent alternating fields with large scale amplitude on nuclei of magnetic materials are studied.

Investigations of line form and hyperfine structure parameters of Fe⁵⁷ nuclei in copper ferrites were carried out by Mossbauer spectroscopy. It is shown that increasing of synthesis temperature leads to redistribution of copper and iron ions among lattice sites. This results in changing of local magnetic fields at iron nuclei and varying of relative intensities of spectrum components. However, detailed study of Mossbauer spectrum line forms for all samples did not allow to detect the influence of nearest cations environment of iron ions in octahedral sites on local field value, which is the case in other spinel structure ferrites. One of possible reasons is strong electron exchange between Cu and Fe ions in octahedral sublattice.

Side-band laser cooling of impurity molecular crystal is considered. The sample is cooling through the system of resonance phonons. The expression for final temperature of cooling is obtained both in low temperature and high temperature approximations. Kinetics of the cooling process are analyzed in weak nonequilibrium case.

The application of laser cooling to facilitate the superradiance process is considered. The possibilities to quench homogeneous and inhomogeneous relaxation processes, to create inversion and to ensure superradiance without inversion are analyzed. The corresponding kinetic equations are constructed. Their solutions are obtained in order to estimate the conditions for observation of superradiance induced by laser cooling process.

Principles of the laser cooling detection by means of photon echo technicians are considered in this paper. The experiment allowing register a degree of short-pulse laser cooling is described in this paper. By means of coherent part of radiating it is realized registration of mode cooling.

A known idea of phase memory based on the optical transient phenomenas in the technician of photon echo is developed in this paper. The results of studies of superslow transient biosystem processes in the technician of shaping the new type echo-response and its characteristics earlier not known are offered.

For a construction of the opto-electronic current transformer the effect of rotating of the photon echo (PE) polarization vector is offered. As an active ambience allowing get the photon echo the vapors of molecular iodine are used. The theoretical model of the opto-electronic current transformer (OECT) is discussed. The explanatory graphs of the n echo polarization vector rotating effect, as well as the principle scheme of the current measurement, are shown in the paper.

Spin echo takes an essential part in the variety of nuclear magnetic resonance experiments. Usually it is considered as the exact reflection of the nuclear magnetization free relaxation decay. The shift between their main spectra lines is discussed in this article.

Results of investigations of the liquid dielectrics, transformer oil in special case, by means of visible optical radiation are presented. On base of these results the express- method of liquid isolating monitoring immediately in filled by oil equipment is suggested.

The comparative analysis of the requirement sensitivity threshold for chromatographic and optical methods of monitoring of gases content of liquid dielectrics was made. There is suggested to use the optical manner for the express- analysis of content of gases in transformer oil. The measurement equipment is mounted immediately on filled by oil electrical apparatus.