Dear colleagues, dear guests from foreign lands, from all over Russia, from Novosibirsk! Let me express my warmest greetings to you on behalf of the Organizing and Program Committees of the Conference. Vavilov Conferences were set up by Academician R. V. Khokhlov in 1969 and over the previous 10 Conferences some traditions have been started and established which have won recognition and respect of the world scientific community. Each Conference was devoted to a limited set of four or five topical problems. At the same time, the treated subjects changed drastically from Conference to Conference and the previous 10 Conferences had covered practically all aspects of the wonderfully variable world of non-linear optics from parity violation in spectroscopy to the optical informational technologies. Summarizing discussions were held on the newly emerging trends and fields. The reports were mostly surveys and had been "ordered" by the Program Committee. The site and time of the Conference have been traditional, i.e. the second half of June, Novosibirsk research center (Akademgorodok). The Organizing and Program Committees of the present Conference were, naturally, willing to maintain these traditions.

A review of interference phenomena caused by a new radiative process, a spontaneous and stimulated transfer of optical coherence (polarization), in absorption, emission, refraction, and scattering spectra. The phenomena are considered using an example of the polarization transfer in spectral doublets and triplets.

Using the laser backscattering method at future TeV linear colliders one can obtain (gamma) (gamma) and (gamma) e colliding beams (photon colliders) with the energy and luminosity comparable to that in e⁺e^- collisions. Now this option is included to conceptual designs of linear colliders. This paper is a short introduction to this field with an emphasis on required lasers which can be used both for eyields (gamma) conversion and for preparation of electron beams (photoguns, laser cooling), some interesting nonlinear QED effects in a strong field which apply restrictions on parameters of photon colliers are discussed.

We describe nonlinear optical processes in a medium with maximal coherence on a Raman transition. The nonlinear polarization of such a medium is of the same order of magnitude as the linear polarization. This allows efficient frequency conversion and generation of a wide spectrum of Raman sidebands. The phase of the coherence can be controlled through a small two-photon detuning from the Raman resonance. An appropriate choice of the phase improves nonlinear generation and propagation of sidebands through an inhomogeneous gaseous medium.

The applications of the new interferometric techniques to the measurement of nonlinear refractive index are summarized in this paper. Developed methods are based on dispersion and shearing interferometry and allow to perform the direct phase measurements in the near field. The majority of the limitations of traditional interferometers have been eliminated in these schemes. At the same time, the benefit of using these methods comparable to currently used is shown for the cases of complicated dependence of the refractive index on the intensity and when the response time of nonlinearity is comparable with the laser pulse duration.

Original results on experimental investigation of properties of reversible long-living optical anisotropy (OA), induced by coherent radiation in glass, are reviewed. Simultaneous action of two mutually coherent light beams with different frequencies (omega) and 2(omega) on an oxide glass leads to accumulation of a long-living anisotropic modulation of the refraction index ((Delta) n-grating). A phenomenon of light self-diffraction under accumulation of the OA and persistent self-sustained diffraction during grating relaxation in the presence of fundamental beam was evidented. Illumination of (Delta) n-grating by external light source speeds up its relaxation. Monochromatic illumination by any beam, leads to photoelectric instability. That is, weak gratings are amplified while strong weaken. A gigantic reversible light attenuation in the (Delta) n-gratings is discovered. Interpretation of the phenomena is based on the phenomenological model of the coherent photogalvanic effect tending to inhomogeneous accumulation of volume charges and reverse influence of static electric field on beams propagation by electro-optical effects.

Microscopic symmetry of ordered media (crystals) manifests itself in an anisotropy of the refractive index. Whereas the internal structure of radiators is taken into account by multipolar expansion, neither radiator size nor lattice grain size ever enters into formulas for the refractive index n of a medium. In optics such an approach is usually well-grounded because of the smallness of these sizes compared with the wavelength (lambda) . Thus, according to the classical Lorentz- Lorenz (LL) formula, the optical properties of an isotropic medium depend merely on the product of a density N of the radiators and the polarizability (alpha) of an isolated radiator. Under derivation of LL formula one assumes the well- known generally accepted connection between a local field vector E' which acts on a separate radiator and mean macroscopic (Maxwell) field vector E:vector E' equals vector E + 4(pi) /3 vector P, where vector P is the mean polarization of a medium. We will show that this relation holds true only for a linear isotropic medium in zeroth (in the medium's discrete parameter) approximation and will derive general relation for arbitrary nonlinear and anisotropic medium with account of its discreetness. It quite naturally leads to modification of LL relation as well.

In this paper we consider an effective variational description for the optical pulse evolution in fiber links with dispersion management (varying dispersion). Instead of solving a nonlinear partial differential equation with varying coefficients, one can gain some important information about the features (e.g. breathing solitons) by an analysis of two ordinary differential equations. This approach provides a clear physical picture of the pulse evolution in a transmission line under the combined actions of nonlinearity, varying dispersion, fiber loss, and periodic amplification. An optical pulse propagation along a transmission line must be periodically reproduced.

We used a new dual wavelength solid state laser system with an extrawide tunability (3 - 19 micrometer) in ps pulses for the study of 'intersubband' resonances in two-dimensional semiconductors, multiple quantum wells, -- using absorption saturation, hole-burning and nondegenerate four-wave mixing spectroscopies. New data on the excited state electron lifetimes and line-broadening mechanism were obtained for different quantum wells widths and compositions.

The title of this presentation uses the expression 'photonic crystals.' By photonic crystals, we mean regular periodic structures with a substantial refractive index variation in one-, two- or three-dimensional space. Such crystals can occur naturally, as exemplified by natural opal, but are more typically fabricated under the guidance of human beings. Under sufficiently strong conditions, i.e. sufficiently large refractive index modulation, correct size of structural components and appropriate rotational and translational symmetry, photonic crystals exhibit the characteristics of a photonic bandgap (PBG) structure. In a full photonic bandgap structure there is a spectral stop band for photonic (electromagnetic) waves propagating in any direction through the structure and with an arbitrary state-of-polarization. This behavior is of interest from both a fundamental physical viewpoint and from the point of view of applications in novel photonic devices. But the physics and device potential of structures which in some measure fall short of ideal photonic bandgap behavior are still of great interest - and it is an important theme of the preset work that non-ideal photonic crystals merit serious consideration.

Second harmonic generation has hitherto been thought of as simultaneous with the excitation pulse which generates it. Recent experiments in Cs vapor demonstrate otherwise. A short two-photon 6D - 6S resonant excitation pulse in Cs vapor generates a superposition state which would radiate immediately were it not for destructive interference arising from the sample being large compared to the radiation wavelength. The radiation pattern of an isolated radiator (atom) starts out with a null in the plane transverse to the polarization (linear) direction but then rotates about the applied transverse magnetic field developing a radiation component along the phase matched direction which we detect. Experimental results are presented in excellent agreement with theory. Previous delay discrepancies have been resolved by using a nonmetallic sample cell. Cascade and yoked superfluorescence take place but not significantly until after the second harmonic emissions. Quantitative measurements of signal intensity are also presented.

Fluorescence detected magnetic resonance (FDMR) coherent phenomena on single triplet-state chromophore guest molecule in low-temperature organic host matrix are analyzed within the stochastic approach to describe triplet electron spin dephasing due to frequency fluctuations U^t induced by host-matrix proton spins dynamics. Exact equations for density matrix of a molecule averaged over histories of the fluctuations U^t are constructed using the model of N random telegraph process. The equations are applied to calculate FDMR responses of a molecule to cw/pulsed MW field and to describe a wide range of available experimental data on (1) the power-broadened FDMR line shapes, (2) the FDMR nutations, (3) the FDMR Hahn echo for pentacene+p- terphenyl pair supposing the fluctuations U^t to be slow. The failure of the standard Bloch equations for this system is demonstrated and the effects of microwaves-suppressed dephasing are discussed.

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) A1/2 SF₆ transition for identical experimental conditions 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.

Non-stationary mechanisms of spatial modulation of luminescence intensity in anisotropic quantum systems within birefringent crystals under their interaction with ultrashort polarized laser pulses were studied. We have found connection between this phenomenon and phase relaxation of excited quantum systems. We have as well grounded a new method for investigation of coherency of quantum systems based on study of characteristic properties of modulation phenomena. It was shown that the influence of the frequency dispersion on the clarity of the modulation picture in insignificant at durations of 100 fs and greater, even for crystals with strong dispersion. Due to the existence of chirp in femtosecond pulses exciting the luminescence, modulation period in instant distribution of absorbed power decreases over distance. In the time-integrated picture of spatial distribution of luminescence intensity, the rate of decrease of modulation depth grows. This leads to new possibilities in experimental investigation of the value of chirp of femtosecond pulses.

Stimulated photon echo technique with specially chosen linear polarizations of pumping pulses of exciting radiation is applied to investigation of depolarizing collisions in molecular gas SF₆ and its mixtures with buffer gases He and Xe. For the first time, the collisional decay rates of population, orientation and alignment of SF₆ levels are determined simultaneously. Translational velocity dependence of orientation and alignment collisional decay rates was under investigation. This velocity dependence proved to be negligible within the frames of experimental accuracy both in pure SF₆ and in mixtures, which is in agreement with standard theoretical approach accepted for depolarizing collisions. Decay rates of orientation and alignment in pure SF₆ have proved lower than velocity changing (elastic) collisions relaxation rate, which allows to conclude, that only some part of elastic collisions participates in destruction of multipole polarization moments of resonant levels. The evidence is obtained for j-dependence of multipole moments relaxation rates SF₆.

The quantum-mechanical transport properties of cold atoms in an optical lattice are described in terms of an analytically tractable model. The atoms are cooled down to the lowest energy band in the periodic optical potential, in the tight- binding limit. The transport mechanisms are coherent tunneling through potential barriers, and momentum recoil at optical pumping. Expressions are obtained for the time-dependent population distributions over the energy eigenstates and over localized states. These expressions are modified in the presence of a dark atomic state, that is uncoupled to the field.

For the first time the optical method of electron-ion plasma cooling, trapping and crystallizing (on microscale) due to laser radiation action on plasma with resonant ions is proposed.

A quantum analytic treatment of the resonant scattering of atoms with j_g equals j yields j_e equals j (j is an integer) transitions by a pulsed (sigma) ₊ - (sigma) _- field is developed. In the approximation of motionless atoms, the atomic density matrix after action of single light pulse is evaluated with exact consideration of the recoil effects. Recurrent equations, which allow to calculate the distribution after arbitrary pulse sequences are found in the analytic form. It is shown that for discrete pulse frequencies the action of N light pulses leads to the formation and narrowing of peaks in discrete points of the momentum space, and also to the broadening of the envelope of the momentum distribution. In the case of the wide (with respect to the photon momentum) initial distribution the explicit formulae for peaks and envelope are obtained and an asymptotic behavior of the solution is analyzed. In the low-intensity limit a dependence of the scattering pattern contrast on the pulse duration is studied.

'White-light' laser cooling of high energy ion beams confined in s storage ring is discussed. The cavity generating the frequency comb is described and the obtained spectra and performances given. The preliminary results on 'white-light' laser cooling of ⁷Li⁺ ions in a storage ring are shown.

In recent years interest has significantly quickened in investigation of nonlinear optical and spectroscopic phenomena in such unique objects as Rydberg atoms (the atoms in the energy states near the ionization limit) and van der Waals complexes (dimers). These objects are characterized, in particular, by that their energy states are strongly degenerate due to a large value of angular (rotational) momentum. Here, the problem arises of adequate theoretical description of experimental results, especially when polarization peculiarities of nonlinear radiation processes are considered. The problem is caused by the existence of a huge number of quantum magnetic sublevels of energy states, which are, in the general case, coherently coupled to each other and take part in the radiation processes. Figure 1 gives a vivid presentation of the problem arising even in such a seemingly simple case when one need describe the radiation transitions caused by a strong monochromatic field between two energy levels with large values of the angular momentum J. If the field polarization is arbitrary, the whole set of the magnetic sublevels turn out to be coupled by radiative transitions. Formally, the problem becomes essentially multilevel. In this case not only the hope fades of solving it analytically using the traditional quantum-mechanical approach, but the problems of numerical solution grow abruptly with increasing quantum number J as well. On the other hand, as is often the case, every cloud has a silver lining. With large J we approach the situation when the rotational motion of particles can be described classically. It turns out that the transition from the quantum description of orientation states of the angular momentum to the classical one simplifies the problem radically: it reduces to the problem of radiation processes in the simplest model of nondegenerate states. In this case the rotational motion manifests itself in a dependence of the density matrix elements on orientation angles of the angular momentum as on a parameter.

In the experiment with barium vapor (close approximation of a two-level system) we found spectra of resonance fluorescence having the form of a pressure-broadened line with a narrow, not collisionally broadened, dip. They are interpreted as the result of collisionally-induced quantum interference among possible spontaneous emission channels of a dressed atom subjected to stochastic perturbation. Also, the analogy between these effects and the coherent population trapping in three-level systems is pointed out.

We have studied sub-natural-width resonances (SNWR) observed in the absorption and fluorescence of Rb vapor under excitation by two copropagating optical waves with variable frequency offset. The mutually coherent optical fields resonantly couple the same ground-state hyperfine level to an excited state. The sub-natural-width resonances present opposite signs depending on which ground-state hyperfine level (GSHL) participates in the interaction with the light. The influence of external magnetic field, polarization and intensity of applied optical fields on the sub-natural-width resonances is examined. The narrowest observed resonance has a width of 10 kHz (FWHM). It is shown that the SNWR obey the selection rules corresponding to two photon transitions starting and ending at Zeeman sublevels on the same GSHL. The application of the observed SNWRs to magnetometers based on the effect of coherent population trapping is considered.

In the present paper we fully analytically solve the problem on optical pumping of atoms by a monochromatic elliptically polarized radiation with taking into account the radiative relaxation of the excited state. It is shown that all dipole- allowed transitions can be divided into four classes with respect to the steady-state solution structure and its physical manifestations. Possible applications of the obtained solution are discussed.

The resonant self-induced optical activity (SIOA) in an atomic alkaline metal vapors has been investigated for the first time. Data on optical polarization rotation are presented and interpreted in terms of the resonance behavior of the third order susceptibility and finite elliptical polarization of real lasers. The limiting action of SIOA on the efficiency of resonance parametric generators and polarization spectroscopy is outlined. The observation of a nonlinear resonant self- induced of the laser beam polarization rotation in ruby crystal (Al₂O₃:Cr³⁺) at the laser transition are reported.

In the introduced paper the results of theoretical and experimental investigations in a branch of probe-field spectroscopy of degenerated metastable atoms in a laser radiation field of arbitrary intensity with taking into account of its anisotropical excitation and the presence of additional channels of radiant decay of upper level are presented. It is shown that for the degenerated levels which are excited anisotropically the absorption spectrum of the probe field contains, besides resonances caused by occupancy effects, resonances associated with the magnetic coherence and manifested in the form of peaks and dips with substantially different amplitudes and widths. A fundamentally new property of these resonances is that their widths are proportional to the intensity of the orienting field, and the amplitude of the narrowest resonance becomes appreciable when the orienting field is very strong.

An analytical expression is found for the profile of Bennett hole with different level lifetimes under strong field and weak collisions. The expression is valid while the diffusion and field broadening being more than the homogeneous one, but less than the thermal width. It is shown that the square of the total width being equal to the sum of the squares of the diffusion and field widths. The shape of saturation curve is calculated including weak collisions. The formula obtained describes the smooth transition from homogenous to inhomogeneous saturation throughout the new intermediate region. Probe-field spectrum of the three-level system is computed in the presence of the strong field at the adjacent transition. The Autler-Townes doublet components are shown to broaden and repel each other under the collisions. The main reason of both the effects occurs to be the diffusion of phase due to quadratic frequency shift.

The elastic light-light scattering below the threshold of the e⁺e^- pair production leads to a variation in polarization of hard (gamma) -quanta traversing (without loss in intensity) a region where the laser light is focused. This effect can be used to exert a full control over (gamma) - quantum polarization. Equations are obtained which determine the variation of Stokes parameters of (gamma) -quanta in this case, and their solutions are given. It is pointed out that this effect can be observed in the experiment of the type of E-144 at SLAC. It should be taken into account and, perhaps, it can be used in experiments at future (gamma) (gamma) colliders.

An influence of nonlinear interference processes at quantum transitions in strong resonance electromagnetic fields on absorption, amplification and refractive indices as well as on four-wave mixing processes is investigated. Doppler broadening of the coupled transitions, incoherent excitation, relaxation processes, as well as power saturation processes associated with the coupled levels are taken into account. Both closed (ground state is involved) and open (only excited states are involved) energy level configurations are considered. Common expressions are obtained which allow to analyze the optical characteristics (including gain without inversion and enhanced refractive index at vanishing absorption) for various V, (Lambda) and H configurations of interfering transitions by a simple substitution of parameters. Similar expressions for resonant four-wave mixing (FWM) in Raman configurations are derived too. Crucial role of Doppler broadening is shown. Theory is applied for numerical analysis of some recent and potential experiments.

Atomic stabilization, the suppression of ionization accompanied by electron localization for increasing laser intensities, was one of the recent predictions for atoms exposed to very intense laser pulses. We discuss a fine structure on such an overall trend of stabilization. We describe how the ionization suppression may be reversed as the intensity is increased slightly. This kind of reversal of the ionization trend takes place repeatedly. We study such reversal of ionization as a function of both laser intensity or frequency. We attribute is origin to the interference of the ionizing wave initiated from various parts of the laser dressed atom.

Review of experiments on microwave spectroscopy of sodium Rydberg atoms carried out during last several years by our group, is presented. Most of the experiments have been done for the first time with Rydberg atoms. These are: static and dynamics Stark spectroscopy, two-photon dynamic Stark effect, double Stark resonance, scattering of Rydberg atomic beam by strong resonant microwave radiation. Also an experiment on pure amplification without the inversion in two-level Rydberg micromaser is discussed.

Coherent control provides a quantum interference based method for controlling atomic and molecular dynamics. We report two experimental observations of different ways to achieve such a control in atomic photoionization continuum. One is the photoionization of sodium atoms, initially prepared in the 3P_1/2 excited state, by a non resonant three-photon interaction with 1064-nm laser light and by a one-photon interaction with the third-harmonic field, at 355 nm. Interference between the two transition paths allows the control of the total ionization rate by varying the relative phase of the laser fields. The second experiment is the observation of the modification of the ionization continua of xenon through laser induced continuum structure (LICS). The multiphoton radiative decay of the xenon ground state into the two electronic continua, that correspond to the two fine structure levels of the ground state of the xenon ion, is varied by electromagnetically embedding a bound state of the atom into the two continua. Both experiments are performed on an atomic beam apparatus which uses a time-of-flight spectrometer for energy analyzing the emitted photoelectrons.

The explicit solution is obtained for four-wave mixing of two strong driving fields at opposite transitions and two weak fields in a four-level system with the large Doppler width. In zero order of the perturbation theory there are two independent two-level systems. A pair of weak fields probe two other allowed transitions. The resonance of the mixing coefficient dependence on intensity is found around equal Rabi splitting in both two level systems. The effect is interpreted as an intersection of quasi-energy levels. Up to 6 peaks appear in the dependence of conversion coefficient on the detuning of the probe field, two of them are a consequence of averaging over velocities and disappear at low temperature. The results allow us to explain the recent experiments on the mixing in sodium vapor.

The atom-dielectric surface interaction in presence of light has been experimentally investigated. A high rate atomic desorption effect induced by light is presented and the most recent experimental results with rubidium and cesium on silane coated surfaces are discussed. The realization of an atomic source controlled by light is presented.

Two-photon light absorption by an atom situated near to surface of a solid with spectral features in the vicinity of resonance frequencies of transitions of atoms is theoretically investigated. These features can be caused, for example, polariton or exiton resonance of a solid. It is shown, that the two-photon light absorption an atom situated near to surface can essentially differ from those in a free space. The spectrum of a two-photon absorption becomes asymmetric over the difference between exciting light frequency and resonant transition frequency of the atom. It is established, that even small spectral features of solid can give rise to significant changes of a spectrum of a two-photon absorption of light. It is established also, that such changes of a spectrum of a two- photon absorption of light are nonlinear increased with increase of the intensity of the exciting light and with approach of the atom to the surface of solid.

The nonlinear spectral lineshape of gas absorption near the solid surface in the field of one travelling monochromatic wave is analyzed theoretically. A 'far' zone of distances to the surface, where coherent particle polarization is formed already after their collisions with surface but interparticle collisions in the gas are not yet significant, is considered. It is demonstrated that the narrow saturation sub-Doppler resonances may be appeared on the Doppler lineshape in this zone. These resonances having no analogues in the gas laser spectroscopy. A formation mechanism of such resonances is discussed.

Nonlinear magneto-optical resonances of the heterogeneous transfer of the charge between atoms, which resonantly interact with the laser radiation, and the surface of the metal or the semiconductor are investigated. The dependence of nonlinear magneto-optical resonances of the surface photoionization of atoms on the values of the angular moment of the energetic levels is analyzed. The possibility of the splitting of the surface photoionization resonance in magnetic field is found.

With modern instrumentation, ellipsometry makes it possible to develop a number of noncontact, nondestructive, sensitive techniques for studies of the structure and composition of thin surface films. Even a minute accuracy in the measurements of polarization angles (psi) and (Delta) characterizing the variations in the light beam polarization resulting from reflection from the object under study, allows the surface film thickness to be determined accurate to plus or minus 0.1 nm, and the index of refraction to the third decimal place. At the same time, the minute accuracy is obviously insufficient to study superthin (under 10 nm) films and to determine numerous unknown parameters of multilayered surface structures. The main obstacle in the way leading to higher accuracy is the lack of the well-developed theory of the instrumentation and reliable metrology basis. The metrology now in use in ellipsometry employs standard samples and averaging of the measured data over four measurement zones. The measured data show a considerable spread over different zones of the instrument which can be attributed primarily to the limited technique adopted for determining the phase compensator parameters as well as to the noticeable anisotropy of the standard sample which is ignored in the 'isotropic' relations involved in the experimental determination of the polarization angles. As a result, the averaged values of the angles (psi) and (Delta) , though slightly improved, are still essentially limited in their accuracy, failing to represent the true properties of the sample adequately. This tendency in metrology does not encourage the improvement in the precision of instrumentation, disguises the anisotropy properties of reflecting systems, eventually limiting the capabilities of the ellipsometry technique. Mostly for this reason, a precision ellipsometer for metrology purposes has not been constructed so far which could be applied in both academic and industrial environments. However, the spread in the experimental angles (psi) and (Delta) over different measurement zones can be regarded as a metrology criterion of the measuring accuracy for the polarization angles, and hence, the accuracy of determining the physicochemical properties of the surface layers. The magnitude of the spread depends on the precision of angle measuring instruments, photodetector sensitivity and measuring accuracy and invariability of all the parameters of the optical elements (mainly, of the phase compensator). This approach underlies the one-zone technique of ellipsometric measurements intended to reduce the spread in the experimental polarization angles (psi) and (Delta) over the measurement zones down to the minimum dictated by the required measurement accuracy. Thus, the one-zone technique is a theoretical basis for the development of reliable metrological control in ellipsometry and the designing of new types of precision instruments.

Due to its simplicity polarization reflectometry technique have some advantages over the ellipsometric methods. We demonstrate this claim in the threefold manner suggesting three novel polarization reflectometry methods for the determination of an optical anisotropy. The first method is based on the measurement of s- and p- polarized light reflectances under near normal or grazing angles (or both) and of the Brewster angle. It may be applied to any uniaxially anisotropic medium. The second method is based on the use of the Azzam Universal Relationship (AUR) between the Fresnel s- and p- reflection coefficients. For a flat surface and an isotropic medium, the Azzam combination of coefficients becomes zero and thus independent of the incidence angle. Finally, for those cases in which the anisotropy of the material of a film deposited on an isotropic substrate is itself of interest a third Interference Method (IM) is suggested. This technique makes use of the different dependences of s- and p- polarized beam optical pathlength changes on the variation of the angle of incidence.

The present work is devoted to the analysis of the ill-posed inverse ellipsometric problem. Manifestations of the incorrectness of the problem are described for the case of ultrathin films. Special attention is given to the choice of the criteria for the optimal point. It is shown that an obvious and frequently used criterion expressed as a condition on difference functional S_o less than or equal to (delta) ², where (delta) is an average error in the measurement polarization angles, is practically useless in our case in the region strong incorrectness. New criteria for the choice of the optimal point are therefore suggested. As a result, the stable solution of the inverse ellipsometric problem is obtained which permits to study successfully the surface films in the thickness range 2 - 10 nm.

The effect of the laser induced nonlinear optical activity in a solution of L-amino acids has been investigated. The experimental data on optical polarization rotation of a laser beam are presented and have been used to determine of the third-order molecular susceptibility for the process of interest. The mechanism which can cause the effect of the nonlinear polarization rotation is discussed.

The method of computer simulations on nonlinear resonant magneto-optical effects developed for real multi-level atoms in the two laser fields of arbitrary intensity and external magnetic field is applied for the polarization effects of different types calculations and investigations of the dependence of the characteristics of these effects on magnetic field strength, intensities, polarizations and detunings of laser fields for alkaline atoms. The essence of the method consists in simulations and analysis of the plots of dependence of quasienergies on parameters (detunings and intensities of radiation fields, magnetic field strength), which are obtained with the help of sorting subprogram, and selection of suitable algorithms for calculations of characteristics of nonlinear resonant magneto-optical effects. One-photon and two photon resonant effects are investigated for wide range of magnetic field strength from Zeeman to Paschen Back effects. Some new features in the spectra of rotation of plane of polarization and circular dicohroizm of different types are predicted. The results show the agreement with known experiments. Such calculations of nonlinear resonant magneto-optical effects in the intense laser fields resonant to adjacent transitions and magnetic field show the opportunity of investigation the modifications of electronic structure due to intense radiation fields and strong external magnetic field in atomic gases and also may be used for the treatment of new methods of phase-polarization selection of modes of tunable lasers.

Backward parametric oscillation (BWO) is a very perspective method to develop mirrorless parametric frquency converters of laser radiation with novel characteristics. As BWO still not been realized in nonlinear optical bulk crystals because of insufficient birefringence, it is worth while testing this effect for waveguide structures. Phase matched solutions for BWO in planar GaAs-ZnSe waveguides have been calculated by use of software carried out for simulation and optimization of three-frequency nonlinear optical processes in planar optical waveguides. In our opinion, some calculated parameters are quite acceptable for a practical realization.

A brief review of the progress in the methodology of chemical design of the acentric crystals is presented primarily for nonlinear optics. The prediction and search of new crystalline phases and compounds have been carried out by the development of the matrix method in binary systems, including the salts of 1-1 and 2-1 electrolytes at first for the lead and barium salt classes. The ion radii and chemical bond lengths have been selected as the criteria in the system analysis of the interrelation between composition, structure and properties. The two areas for an initial search of new nonlinear optical materials have been proposed: the oxide salts with the short or long chemical bond length. For example two new binary nonlinear optical iodate crystals have been predicted and synthesed.

The contribution of internal electronic shell into the infrared radiation is under consideration. It is shown that this radiation may achieve great value when atomic oscillations are synchronized by the sound wave.

Properties of a crystalline passive Q-switch based on F₂⁺(A) color centers in Li doped NaF for the ruby alexandrite lasers are presented. Preparation, spectroscopic and Q-switching characteristics (in these lasers), termo- and photostability of F₂⁺(A) color centers are considered. Q-switches properties increase with photochemical reactions help is discussed. Possibility of passive Q-switches creation for lasers on lantanoids, Cr, Ti ions in various crystals with radiation wavelength 0.7 - 1.0 mkm is showed.

Amplification of stimulated Raman scattering (SRS) radiation of ethanol in a polydispersion of microdroplets of ethanol solution of Rhodamine C is obtained experimentally when irradiating the droplets with laser pulses of 0.532 micrometer wavelength.

In the present paper we analyze the results of our experimental investigations of nonlinear dynamics of the free generation of the ions of chromium and neodymium in the various media. The results of the theoretical investigations of the role of the dynamic Stark effect and stochastic factors are produced in the generation forming.

The dispersion of cubic optical susceptibility of submicron films of pseudoisocianine J aggregates are measured by a z- scan technique. The values of Im(chi) ⁽³), Re(chi) ⁽³) near to J-peak were approximately 10^-5 esu. The measurements have shown that the films near to J-peak have negative sign of Im(chi) ⁽³)((omega) ), which corresponds to nonlinear bleaching of absorption. The maximum Im(chi) ⁽³)((omega) ) is observed for (omega) approximately equals (omega) _J. It is found that at low frequency side of J-peak the sign of Im(chi) ⁽³)((omega) ) changes on positive. The measured dependence Re(chi) ⁽³)((omega) ) has compared with the value calculated by Kramers-Kronig transformation. For optical dense samples the contribution of a thermal nonlinearity is displayed. The spectral behavior features of Re(chi) ⁽³)((omega) ) and Im(chi) ⁽³)((omega) ) are explained by four-level model of Frenkel exciton.

Manifestations of two photon photo-effect at illumination intensities on the order of solar light (10^-3 W/cm²) were observed for the first time. We believe that it is due giant enhancement of the nonlinear effects in the local fields, inherent to fractal nano-structures.

The nondegenerate three-wave process of second harmonic generation under exact phase matching and of different amplitudes and polarizations of interacting waves is considered experimentally in KTiOPO₄ crystal. The central part of the weaker pulses of fundamental frequency and of the second harmonic oscillates periodically both in spatial and temporal domain. The complete transformation to the second harmonic and back, accompanied by (pi) -changing of the phase of carrier frequency, at every cycle is observed. Clear beam canalling is observed too.

Exposures of oxide glass to two coherent light beams with different frequencies (omega) and 2(omega) leads to the buildup of spacial index gratings in the glass. This gratings are instable and can be amplified when the glass is illuminated only radiation with the fundamental frequency. In this letter we are reporting about new instability. We observed amplification of the refractive-index when glass was illuminated only second harmonic radiation of the laser. The results of the experiment can be explained by a model of a coherent photovoltaic effect. Mechanisms of the limitation of instability are analyzed. It is assumed that the limitation of the instability is as a result of increasing of the second harmonic radiation absorption, when the refractive-index is intensified.

On our experimental research we observed the amplification and relaxation of optical anisotropy in the glass, induced by the bichromatic radiation, when the glass was illuminated only radiation with the fundamental frequency. The amplification of the anisotropy is established by the degenerate three-waves interaction and the return link, appearing because of the coherent photovoltaic effect. The stationary stable modulation of the refractive-index is depended on the intensity of illumination. The gigantic increase of the second harmonic radiation absorption in the photoinduced gratings was observed. The hypotesa of the demphing of the instability and the building of the stationary periodical gratings of the refractive-index is suggested.

A theoretical and experimental investigation was made of the mechanism of formation of a lengthened train of pulses in a garnet laser. A comparison of the theoretical and experimental results indicated that the mechanism in question was associated with the absorption by free carriers when the laser cavity with hybrid mode locking, contained a negative-feedback component in the form of GaAs.

We study the phenomenon of the spontaneous soliton formation (SSF) emerging under the propagation of a high-power laser pulse, being initially non-soliton, through a two-component resonantly absorbing medium. By the SSF we mean a process of self-forming of soliton-like optical pulse (or pulses) from initially non-soliton one in the course of its propagation through the medium. The further propagation of this soliton- like pulse is accompanied with the zero energy dissipation.

The effect, determining non-linearity of gain in semiconductor lasers, is described. This nonlinear effect works, when saturation effect doesn't work. The effect was taken into consideration for calculation of light output power and threshold current.

Results of investigation of a Ti:Al₂O₃ laser with cryogenic cooling and pumping with a high-power Ar⁺ laser of the MIL type are presented. The results show that Ti:sapphire laser with high-power multimode argon laser pumping can provide output powers on a TEM₀₀-mode (at least greater than or equal to 40 W) with a high conversion efficiency. In effective cooling conditions the emission spectrum of such a laser with a resonator without selecting elements consists of one or several peaks approximately equals 2 nm wide.

New approach to construction of the compact femtosecond system is proposed. This system can provide less than 50 fs light pulses with up to 100 (mu) J energy and more than 500 Hz repetition rate in visible, near UV and IR spectral regions. There are some essential advantages of this system in comparison with traditional solid state amplifiers schemes. First of them is a possibility of self-selection of incident femtosecond pulses, second is a self isolation of amplifier from master oscillator. Than, weak self phase modulation and chirp broadening of pulses in thin dye cells which promise us to use simple prism pulse compressor, and finely is an amplification second harmonic radiation (violet-blue radiation). Amplified violet-blue femtosecond pulses can be used than for pumping of optical parametric oscillators (OPO) and amplifiers (OPA) on the base of LBO, BBO or LiJO₃ crystals. Femtosecond pulses at the signal frequency from that OPO can be also amplified in multipass dye cells, pumped by the same N₂ laser. Because beams in channels are simultaneously, it not need to use in this scheme start discharge electronic synchronization systems. Amplifiers parameters estimates give reason to expect that this version of femtosecond system will have smaller sizes and price in comparison with well known existing now on the market femtosecond systems, which provide femtosecond pulses less than 50 fs, with energy up to 100 (mu) J and repetition rate more than 500 Hz in visible, near UV and IR spectral regions.

The dependence of nonlinear resonances of two-photon scattering on acoustic vibrations in gases is investigated on the polarization of the laser radiation, the angular moment of the energetic levels and magnetic field.

The experiments on transient phenomena in pulsed optical orientation of Rb atoms by the emissions of semiconductor lasers are presented. With using probe field method it was found that macroscopic magnetic momentum induced by strong pulsed laser field is processing in weak magnetic field causing Larmor oscillations of the absorption coefficient of probe field. The same effect was observed at fast changing of direction of the magnetic field.

The ground electronic state of even such simple atoms as those of alkali elements has the set of sublevels. These sublevels are hyperfine (HF) components and magnetic sublevels. The collisions with particles of nonmagnetic buffer gas or even with walls (when walls have proper coating) do not mix practically the populations of ground state HF sublevels, if the orbital moment of electrons in the ground state is equal to zero. Due to this reason these sublevels may be extremely long lived. Because of this, for instance, the so-called effects of optical orientation and optical pumping are apparent in atoms of alkali metals. The radiation can pump practically all the atoms (with which there is effective interaction) to a single HF component. In a situation in which optical pumping is a minor effect, the monochromatic absorption line consists of separate lines corresponding to intra-atomic transitions. The optical pumping is not significant, for example, if the radiation intensity is so low that now pumping between HF sublevels occurs in the time it takes the atom to traverse the light beam. Under the conditions of optical pumping and when other nonlinear effects are present, the absorption line profile can undergo considerable alteration. Many theoretical and experimental investigations have been done in the laser spectroscopy of resonant transitions of atoms (atoms of alkali metals) under the conditions of optical pumping within ground state HF structure. A characteristic feature of all such investigations is the velocity-selective excitation of absorbing atoms. Also, as a rule, the value of HF splitting is not very big in comparison to Doppler broadening in these experiments. Under such conditions, the absorption spectra consists of Doppler- broadened lines with nonlinear resonances, which emerge when two fields of different frequencies or different propagation directions are employed. When only one monochromatic traveling wave is employed, optical pumping leads to formation of a single smooth absorption line occupying a position between the resonant transitions frequencies associated with HF components. As HF splitting grows, the line profile remains smooth, its width is approximately equal to the size of the HF splitting. The strength of the optical pumping from one ground state HF component to another is greater for greater HF splitting in comparison to the Doppler width. In this regard, Cs and Rb are the most typical of the alkali atoms (the HF splitting exceeds the Doppler width by a factor close to 20). This is the qualitative picture of the absorption line profile (particularly for a monochromatic radiation) under the conditions of optical pumping between the HF sublevels of the electronic ground state, this qualitative picture had formed by now.

An absorption coefficient and hence the population density of metastable states 3d⁴F, 3d²P, 3d'²G were measured by a single-frequency dye laser in gas-discharge plasma. It has been shown that population distribution between levels of multiplet 3d⁴F_J can be described by Boltzmann's low with temperature close to that for heavy particles. Relaxation constants measured from absorption saturation curves have close values for different metastables and are approximately equal to (Gamma) _n approximately equals (2 divided by 6) X 10⁷ s^-1. High value of relaxation constants means high excitation rates of metastable levels. Linear dependence of (Gamma) _n on electron density was shown for 3d⁴F_7/2 level. It has been demonstrated that electrons are of great importance in the deactivation process. The measured parameters of levels are used for evaluation of output characteristics of three-level Raman laser with metastable start and final levels.

The light force on slow atoms in a light field with arbitrary polarization distribution is explicitly evaluated in the case of an atomic transition J yields J with half-integer J values. The expression of the force is based on an exact analytical expression for the steady-state density matrix of the atoms. The force is naturally separated in contributions resulting from gradients of the field intensity, the polarization ellipticity, and the phase. In addition to a conservative part this force also contains a vortex component. In areas of spatial localization, where the total force vanishes, the atomic motion is governed by a potential, which in general is not harmonic for J greater than 1/2. Simple model of the formation of a one- or two-dimensional spatial atomic grating in a specific light field configuration illustrates the results.

Results of investigations of high excited states of a quantum anharmonic oscillator in close to dissociation boundary are represented. Using the quasienergy method we are obtained an equation for the calculation of energy spectrum in the quasiclassical region. This equation is solved numerically. The main results are as follows: (1) At N less than 10⁷, where N is the quantum number, the dependence E_N on (omega) has a character of a diffusion and asymmetric peak in close to the resonance frequency. The peak is higher, if an amplitude of a field is the higher. (2) At N greater than 10⁷ the dependence E_N((omega) ) has an oscillation character and also quasicrossings of energy levels take place.

Integral cross-sections ((sigma) _int) of the absorption of the ground (²P_3/2) and excited (²P_1/2) fine structure states of atomic iodine have been measured for four transitions in the VUV region: ²P_1/2 - (³P₂)6d[1]_3/2; ²P_3/2 - (³P₂)5d[0]_1/2; ²P_3/2 - (³P₂)5d[2]_3/2 and ²P_3/2 - (³P₂)5d[2]_5/2. The oscillator strengths derived for these transitions are: f₁ equals 0.047 plus or minus 0.011, f₂ equals 0.0088 plus or minus 0.0026, f₃ equals 0.029 plus or minus 0.007 and f₄ equals 0.053 plus or minus 0.014, correspondingly.

We study resonant four-wave mixing process (omega) ₄ equals (omega) ₁ minus (omega) ₂ plus (omega) ₃ under conditions of coherent population trapping (CPT) when radiations with frequencies (omega) _1,2 are strong, and (omega) ₁ minus (omega) ₂ equals (omega) ₂₀ ((omega) ₂₀ is a frequency of electrodipole-forbidden transition). It is shown that under the CPT sufficiently large nonlinear polarization (the same as linear polarization or higher) may be created. We show that in atomic Ba vapor for cw lasers quantum conversion efficiency can be as high as several tens percent.

The kinetics of atoms with the degenerated excited and ground states in an elliptically polarized wave is considered. In the simplest case of the 1/2 yields 1/2 transition it is shown that all kinetic coefficients essentially depend on the light ellipticity. In particular, in the low-saturation limit the friction force contains, apart from the well-known Doppler friction, a term that arises from a transition between adiabatic potentials and can be interpreted as the Sisyphus friction.

Three-wave frequency mixing is theoretically investigated under simultaneous single- and two-photon resonances; one of the fundamental fields is weak while another one is strong. The influence of field splitting on nonlinear susceptibility is studied for both homogeneously- and Doppler-broadened transitions. We analyzed the role of interference of quantum transitions via quasilevels in absorption and nonlinear generation and its impact on mixing process. The possibility of significant enhancement of nonlinear generation efficiency in optically dense media is demonstrated.

The results of multiphoton ionization of the Yb atoms in a long atomic beam near the autoionization (AI) level 4f¹³6p²6s and determination of the Fano parameters of AI resonance are reported. The possibility of the amplification without inversion producing near the AI Yb atom levels is analyzed.

The method is developed which allows to descript spontaneous and Mandelstam-Brillouin stimulated scattering both in the frames of one model approximation.

A theory allowing to describe of quantum chaos in the term of nonlinear classical dynamics is proposed. It is showed that a solution of a quantum problem in quasiclassical region is connected with a solution of a corresponding classical problem which is the classical limit of the quantum one. It is showed also that the wave function phase is satisfied an own equation of motion and it is a classical dynamic equation. Dynamical chaos of nonlinear classical dynamics results to irregularity of the wave function phase and a strange attractor in a classical dynamics of the wave function phase leads to irregularity in probabilities of transitions of anharmonic oscillator in an external time-dependent field. In the pure quantum and the pure classical region corresponding solutions are independent.

We investigate the line narrowing in dense plasmas due to ion- ion scattering. Landau term include velocity dependence of the effective transport collision frequency that makes the problem more complicated that the Dicke narrowing in gases. The collision process is analytically described as a diffusion in the velocity space. It is shown that the atomic density matrix can be calculated by decomposition over orthogonal polynomials. The analytical results are obtained in limiting cases of short and long wavelength compared with the mean free path of an ion. For intermediate case a simple interpolation formula, based on numerical calculation, is proposed having an accuracy within 10% both for absorption linewidth and anomalous refractive index. The conditions for experimental observation of the narrowing are discussed.

In the present study, the magnetic field influence on the NO fluorescence induced by the B²(Pi) ((upsilon) equals 0) yields X ²(Pi) ((upsilon) equals 9) transition was investigated upon the direct population of the B²(Pi) ((upsilon) equals 0) level by the processes: NO[X²(Pi) ((upsilon) equals 0)] + N₂(A³(Sigma) ⁺_u) yields NO]B²(Pi) ((upsilon) equals n)] + N₂; NO[B²(Pi) ((upsilon) equals n)] + M yields NO[B²(Pi) ((upsilon) equals 0)] + M; and by the aforementioned processes together with the processes: NO[B²(Pi) ((upsilon) equals 0)] yields X^{2$ (Pi} ((upsilon) equals 9) + hv_fl; X²(Pi) ((upsilon) equals 9) + hv_exc yields NO[B²(Pi) ((upsilon) equals 0)]. Data observed in the present study and published in literature were explained by the model including 'gateway' mechanism, developed by Ottinger and Vilesov, in combination with the magnetic field coupling mechanism of the rovibronic levels belonging to the B²(Pi) ((upsilon) equals 0) and X²(Pi) ((upsilon) equals n) states. In a frames of this model, it was assumed that the fast collision-induced transitions are realized between the rovibronic levels of the B₂(Pi) ((upsilon) equals 0) state.

Extremely large e.m. fields can be generated in plasmas by high intensity laser pulses. Several aspects of their generation and of their effect on the plasma and on the laser pulse have been discussed recently. In particular, the nonlinear interaction of an ultraintense laser pulse with a thin foil modifies the shape, the frequency content and the polarization of the pulse. A 2D3V particle in cell code has been developed and its characteristic features are described. Two examples of the results obtained are presented. These simulations show that the relativistic transparency of a thin foil leads to the sharpening of the laser pulse. In addition they show that a quasistatic magnetic field is generated at the foil surface.

Basic principles of weak echo-signals laser receiving are briefly summarized and autodyne lidars employing this way of weak signal detection while sounding the atmosphere are described. Detection of weak light signals by a hybrid laser is studied theoretically and experimentally. Autodyne lidar modifications, namely the multipurpose cw parametric autodyne lidar which allows one to increase a set of retrieved from the received by the laser echo-signal optical and dynamic characteristics of an atmospheric path and a remote retroreflector and a hybrid lidar in which positives of conventional cw autodyne lidars are combined with those inherent to pulsed lidars are discussed

It is shown that in the dark magneto-optical lattices the effects connected with the Bose-statistics of particles can be observed under the laser cooling temperature (10^-4 - 10^-6 K), that is orders of magnitude higher than the evaporative cooling temperature in magnetic traps. There appears the quasicondensation, when the wave function is formed at the localization distance of atoms in a single well. Apart from this, we show that the adiabatic reducing of the magnetic field leads to the increasing of the temperature and the Bose-condensation in the whole lattice can take place. The field configuration, where the form of the three-dimensional magneto-optical potential does not depend on phases of light waves, is found.

The dark magneto-optical lattice for atoms with a J yields J - 1 transition is considered. The periodic potential is formed using a (sigma) ⁺ - (sigma) ^- laser field and a uniform magnetic field orthogonal to the light waves propagation. The dynamics of slowly moving atoms was investigated for J equals 1 in the quasiclassical approximation. The sub-Doppler cooling for a blue detuning from resonance is demonstrated. The dark atomic lattice creation in the case of the light induced shift is much less than the Zeeman splitting is predicted.

The interaction of high power laser radiation with the atoms in the external magnetic field leads to the new nonlinear effects due to modifications of populations of the states of the system 'atom plus field.' From one side it can be followed by new peculiarities in the effect of the coherent population trapping and from other -- the effects of the population modifications are important for explanation of regularities of nonlinear magneto-optical effects. The modification of population dynamics due to the parameters of the system -- radiation field intensities, detunings, polarizations, magnetic field strength and orientation, relaxation constants leads to the new features in polarization effects, resonant fluorescence and resonant Raman effects. The new features of the considered theory are that it is built for multilevel atoms and has not restrictions on the probe intensity compared to the pump intensity. The theory and method permit to investigate the populations modifications depending on modifications of the parameters of the system and to find the relation between population dynamics and new nonlinear resonant magneto-optical effects. The considered system consists of atomic gas of low concentration in the constant magnetic field and two monochromatic laser fields of different intensities and polarizations. Analytically the influence of magnetic field on population dynamics of three-level systems have been considered. For real multilevel atom the computer simulations show the dependence of population dynamics on relaxation constants and the differences of this dynamics for different magnetic sublevels of the excited states of the atom. The results agree with known theoretical and experimental works.

Recently, the existence of population-trapping states in a two-level system driven by a frequency-modulated field has been demonstrated. In this work we show such states can exist in a two-level atom driven by both an amplitude- and phase- modulated field.

There were examined photoionization spectra of benzene cooled in supersonic molecular beams. Compounds of benzene vapor with several buffer gases were used -- He, Ne, Ar, Kr, N₂, CH₄. The photoionization was performed by frequency tuning KrF laser (linewidth 0.8 cm^-1; tuning range 120 cm^-1). The process is step-by-step, with the real intermediate level. The tuning range envelops two vibronic bands 6₀¹1₀¹16₁¹ and 6₁¹1₀³, belonging to electron transition ¹A_1g - ¹B_2u. The ionization spectrum is mainly dependent on the absorption spectrum at the first step. The both bands are hot, but nevertheless the ionization efficiency at supersonic beam conditions is rather high; it's caused by large 'gap' of vibronic temperature from rotational and translative ones. As it was experimentally defined with various buffer gases, that bands intensity relation varies too. This fact testify about vibronic cooling dependence on the sort of buffer. Besides, a significant difference in the bands envelope contour widths was discovered. That is rather unusual fact, as the band width mainly depends on rotative temperature in the low state (rotative band structure wasn't resolved in that experiments). Based on their data the rotative temperature estimation shows for benzene, that rotative temperature of molecules with excited 6^th vibronic mode is always lower (approximately equals 4.5 K with Ne buffer), than molecules with 16^th one (approximately equals 15 K at the same conditions). This fact was interpreted as the rotationally-vibronic interaction result. As degenerated 6^th mode has vibrational angular momentum, which is absent in the 16^th, degenerated as well, so rotative-vibronic interaction in the first case is significantly strong, and leads to levels splitting comparable with the rotative structure. As the result rotative levels density for 6^th mode twice more. The interpretation moment for rotative relaxation, i.e., the time, or characteristic distance from the nozzle cut-off, where rotative relaxation in the molecular beam forming on translative temperature and molecular density as well as sublevels energy interval. The last is twice less for molecula with the excited 6^th mode, that is the reason of their more intense rotative cooling.