At our conference A. M. Prokhorov and I are assigned the role of Conference Chairs. As far as I understand, the chair of the conference in his obligations is, to a considerable degree, like, say, the King of Belgium or Sweden. The main responsibility of the King is to pronounce the King's Speech. Respectively, the Chair of the Conference is obliged to pronounce the opening speech. The King in his speech usually remembers the glorious periods in the history of the state and emphasizes its greatness to give pride to the subjects' hearts. Also, the chair should recall in his speech some achievements in the work of the conference. The participants of the conference should be assured that they are attending a reliable scientific undertaking rather than some risky adventure like the MMM company. This talk undertakes to accomplish all that.

The contribution of laser-induced thermoelectric effects in the formation of periodic relief on the surface of metal and metal-like melt is considered theoretically. The threshold and the instability increment are found.

In our analysis, the Archimedean and thermocapillary mechanisms (or subsystems) are complicated by the superposition of the thermoelectrical subsystem, leading to a new technological opportunity, which is the transport of heat by cellular motion when heating is from above. The interaction of the subsystems determines the properties of the object which is the molten zone. Synergetic properties of the object and its space-time periodicity are governed in particular by the thermoelectric instability and by the thermocapillary stabilization. It follows that the Thermoelectric convention is an example of the interaction of hydrodynamic, electric, and thermal subsystems in a disordered system. When these subsystems interact in an open thermodynamic system, such as a heated liquid film, self- organization takes place and macroscopic space-time structures appear. It follows from synergetic consideration that the resultant cells (deterministic motion) also exist in a certain range of values of the same control parameters. The new mechanism explains why it is possible to transfer heat by convection when a free surface is heated. This problem is important in the formation of melts by laser radiation.

Mechanoluminescence and thermal radiation induced in the back side of metallic targets irradiated by a laser pulse were investigated. Neodymium glass laser was used (lambda equals 1.06 micrometer, duration of pulse 1.2 ms, beam diameter 2 - 5 mm); two detective systems: (1) photomultiplier with sensitivity of 10^-16 W in the region 300 - 800 nm; (2) photoresistor with sensitivity of 10^-10W in the region 800 - 1500 nm; gold, silver, platinum, copper and titanium targets 1 - 0.1 mm thick, 40 mm diameter and investigated optical radiation (luminescent and thermal) from back side of target as function of laser pulse energy, number of laser pulses and structure (density of dislocations) of target material. The luminescence and thermal radiation of target back side were registered. The laser pulse energy was quite small: P_las approximately equals 0.2 P_th (P_th - energy threshold of the sample). The evolution of luminescence by cyclic irradiation was observed. It is demonstrated that the excitation of luminescence depends on the initial structure of the metallic target on the density of dislocations.

A dynamic holographic technique based on two phase-modulated coherent optical bemas mixing was applied for a photoconductor polyimide-liquid crystal structure investigation. Deep modulation of the output beams intensities confirmed high optical non-linearity of these structures. A spatial mismatch between the beams interference pattern and the recorded grating was observed indicating the liquid crystal molecules orientational anisotropy. The kinetics of holographic gratings recording and erasure demonstrated a complicated non-monotonous behavior which could be a result of the photoexcited electric charge drift and diffusion.

We report our results of experimental study of photoelectrical properties of GaAs p-n and l-h junctions illuminated with pulsed carbon-dioxide laser light. The current-voltage and voltage-power characteristics are investigated. It is demonstrated that photoemission of hot carriers across the potential barrier and the crystal lattice heating are the dominant mechanisms in the photovoltage formation. The obtained results show that hot- carrier effects in inhomogeneous GaAs can be used to detect very short infrared laser pulses.

The process of channel formation during hole punching in glass by pulse-periodic radiation of carbon-dioxide laser has been experimentally investigated with due account of modulation of radiation that passed through the keyhole under deep penetration conditions (ratio between hole depth and diameter was 3 divided by 10). The frequencies of keyhole walls vibrations in the course of punching and velocities of channel radius variation have been measured. In the experiment, the phenomenon of periodic structure formation on the channel walls under the action of carbon- dioxide laser pulse-periodic radiation has been revealed.

Two mechanisms of substance rearrangement originating from pulsed laser radiation are considered. The first is connected with inhomogeneous laser intensity distribution. The second is related to cavitation processes in the substance under sufficiently powerful laser radiation.

The theoretical model of hole punching by laser radiation is submitted. It takes into account the basic laws of radiation absorption by the walls of the channel. This model describes the dynamics of the form and depth of the channel, as well as presents the known and obtained experimental data on hole punching in metals and dielectrics.

The influence of the following on running air flow upon the velocity of hole punching in glass has been investigated under the action of pulse-periodical carbon-dioxide laser radiation over the intensity range from 40 to 300 kW/cm². The power density range has been determined that is favorable to the penetration regime.

Semiorganics are emerging as an important class of nonlinear optical materials. These combine the high optical nonlinearity of the organic materials with the better device handling properties of the inorganic materials. The results of our experiments on the laser induced damage in semiorganic NLO crystals are presented here. The results on our successful attempts to improve the resistance to damage in these materials are also presented.

A model description of the laser-induced free carriers influence upon the point defect generation and optical damage in the wide-gap semiconductors and dielectrics is presented. The model is based on the following assertions: (1) The defect creation probability in solid considerably increases compared with its usual temperature-fluctuation value if the free carriers are involved in defect generation process (so-called recombination-stimulated defect reactions); (2) The point defect creation in crystal resulting in energy spectrum transformation leads to free carriers generation in solid even without the lattice heating. The positive feedback between free carrier and point defect concentrations stimulates the fast increase both carrier and defect densities and under certain conditions results in optical damage of crystal. The conducted analysis makes it possible to assert that: (1) The optical damage of transparent solids is often due to the electron-stimulated defect reactions arising under the wide range of light irradiation parameters; (2) The above mentioned process of the defect generation must be taken into account in the analysis of 'accumulative effects' in low absorbing media under multiple laser action with sub- threshold intensities.

While the optical breakdown of transparent dielectrics for nanosecond and longer laser pulses is well investigated theoretically and experimentally, the breakdown in a field of picosecond and femtosecond pulses has not been adequately explored. At the same time such investigation presents scientific interest, because short pulse duration can make some change for a mechanism of the optical breakdown. Also these data have practical importance for high energy laser development and management of temporal parameters of a pulse. Thus we have carried out measurements of the damage thresholds for pulse durations 450 ps and 3 ps (FWHM) for fused silica. Theoretical analysis is presented to explain experimental results. The possibility of applying the optical breakdown for pulse shortening is discussed.

The present report gives an account of experimental investigations of coatings damage under laser radiation (LR) action. Q-switch modulation ((tau) _i0,5 equals 30 ns) and free generation (total impulse duration (tau) _i equals 170 microseconds) regimes of Nd-laser working were used in the experiment. The energy thresholds are determined for seven samples with different coatings. Some notes to research test scheme, principles of results processing, physical description and discussion of research results are contained in this paper.

Kinetics of luminescence flashes (LF) accompanying optical breakdown development in volume of alkali halides crystals under the action of carbon-dioxide laser radiation pulses with intensities near by the threshold of LF appearance (approximately 10 MW/cm²) has been studied. LF shape and intensity have been investigate under the action of the first and subsequent pulses on the same place of the specimen. It has been observed that LF consist of large numbers of more or less resolved spikes with duration at least approximately 100 ns (or less) which has been determined with time resolution of the used apparatus. It has been shown that peculiarities of observed LF kinetics cannot be explained on the base of conclusion about their thermal nature and do not contradict conception of tiboluminescence and its irregularities. Triboluminescence is a result of crystal fracture (in crystal areas, surrounding absorbing inhomogeneities) under the action of thermal stresses caused by absorbing inhomogeneities temperature growth.

Alkali adsorption on the surface of the monocrystalline sapphire was studied by means of laser stimulated desorption. The photo-desorption yield was found to be proportional to the laser fluency up to the threshold of the thermo-desorption process. The feature of the experimental apparatus was the possibility to control the coverage by means of the surface temperature provided the adsorbate was in dynamic equilibrium with a vapor of constant pressure. It was found that alkali atoms are adsorbed mostly on the centers with the surface concentration of about 10¹³ cm^-2. Although the temperature dependence of surface coverage is consistent with the conventional Langmuir model for adsorption on the isolated centers, the estimated adsorption energy of about 1 eV is too large to account for the quantum yield of photo-desorption process which is as high as 5 multiplied by 10^-5. To resolve this contradiction we assumed that adsorption centers make up chains along the steps on the surface. Lateral interaction between neighboring adatoms were accounted for by means of methods developed for Ising model. Theoretical results are in agreement with the experiment.

The role of environment in modification and etching of polymethylmethacrylate (PMMA) films by the fifth harmonic of Nd laser is investigated experimentally. The theoretical model is developed, which describes the main features of modification and etching kinetics for sufficiently small laser fluences.

Leaky-wave type Wood's anomalies due to excitation of guided waves on the dynamic grating induced in the thin nonlinear liquid-crystal slab are studied. For the first time the existence of Wood's anomalies in carbon-dioxide laser radiation self-diffraction on a reflecting liquid-crystal cell is shown by theoretical and experimental investigation of excitation of surface polaritons in plus 2 and minus 3 diffraction orders and leaky interferometric modes in plus 1 and minus 2 diffraction orders.

Lateral self-limitation of the cw-laser-induced local oxidation of ultrathin (3-60 nm) titanium films in air is studied. It is shown, that the brightening of the films on transparent substrate upon through-oxidation forms a negative feedback to this highly-nonlinear process allowing stable writing of transparent oxide line structures narrower than the diffraction limited focused laser spot. The optimum metal film thickness to obtain the greatest optical contrast with the highest resolution is of the order of the light adsorption length in the metal. Transparent isolated oxide lines and gratings with periods down to 250 nm and line width down to 165 nm were recorded in 6 - 15 nm thick Ti films on glass by using the radiation of the Ar ion laser (lambda equals 488, 514 nm).

Understanding the processes underlying the optical excitation of atomic vapor in the vicinity of solid surfaces is of interest both from physical and technical points of view. Selective reflection spectra of laser light from an interface of a transparent dielectric material and resonant vapor are known to be Doppler-free and to provide important spectroscopic information about the atom-wall interaction. On the other hand, atomic vapors have such a large and fast nonlinear response on or near resonances that they are capable of processing signals and images with milliwatt lasers at a time scale of submicroseconds. In the present paper we investigate linear and nonlinear optical properties of a thin film of atomic vapor confined between two solid surfaces. Assuming two-level atoms, we solve the Maxwell- Bloch equations for light reflection from resonant atoms. The interaction between the resonant atoms and the wall is accounted for through the boundary conditions for all elements of density matrix. The transient polarization is shown to make an important contribution not only to the field structure in the vicinity of the wall but also to the interference pattern of the reflected field. It is found that the spectrum of reflection depends remarkably on the film thickness. Strong enhancement of signal is also found from this study and possible devices for the detection are discussed.

The two-exposure schliren-method was used to determine parameters of shock waves generated in the water and air by the pulsed carbon-dioxide laser radiation focused onto the free surface of the water. The pressure on the shock front was calculated from the experimentally obtained data for the shock front velocities. The scattering zone has been found to be formed directly under the focal spot which at early stages of the process expanded with a velocity significantly exceeding the sound velocity in the water. This paper deals with the study of shock waves generated in the water and air by the pulsed carbon-dioxide laser radiation focused onto the free surface of the water. The two-exposure schliren- method was used to determine parameters of shock waves. The optical scheme of the experimental set-up is presented.

Different types of laser processing can significantly increase the corrosion resistance of constructive materials, secure higher levels of metal properties in comparison with standard protection from corrosion and can be successfully used for industrial application. The research carried out in TRINITI during the last 10 years allowed us to create a data base about corrosion behavior in different chemical media of various metals, alloys and steels after welding, melting, surface alloying, etc. on technological continuous-wave carbon-dioxide-laser with average power up to 5 kilowatt. The investigated materials were subdivided into two groups: (1) without changes of phases composition after laser processing (pure metals, stainless steels); and (2) exposed to structural and phase changes under laser-matter interaction (carbon steels with different carbon content). It has allowed us to investigate the peculiarities of corrosion process mechanism depending on matter surface structure and phase composition both on laser irradiation regimes. Our research was based on the high sensitive electrochemical analysis combined with other corrosion and physical methods. The essential principles of electrochemical analysis are next. There are two main processes on metal under the interaction with electrolyte solution: anodic reaction -- which means the metal oxidation or transition of metal kations into solution; cathodic reaction -- the reoxidation of the ions or molecular of the solution. They are characterizing by the values of current densities and the rates of these reactions are dependent upon the potential arising on the metal-solution frontier. The electrochemical reactions kinetic investigations gives a unique possibility for the research of metal structure and corrosion behavior even in the case of small thickness of laser processed layers.

The temperature to which thin chalcogenide film is heated by a light pulse with a minimum power causing destruction is shown to exceed substantially the melting temperature of the material. Local destruction of films under the action of electric current or light may be characterized by a critical power W_c, i.e., a minimum power causing the destruction of a material. This parameter determines the limiting power level that amorphous films used in memory devices, waveguides, and switches can withstand. The mechanism of destruction is conventionally related to a temperature rise. No reliable methods exist for measuring directly the temperature T_c to which a film is heated by a short light pulse with power W_c. In this connection we evaluated T_c from the dependence of W_c on pulsed exposure duration and also by comparing W_c with the power levels which induce melting or crystallization, occurring in the temperature interval well-known for long exposures. We used as objects of study films of the chalcogenide glass Ge₁₅As₄Te₈₁ of thickness L₁ equals 0.15 - 0.3 micrometer, prepared by vacuum evaporation on glass substrates. Films of this and similar compositions show a reversible glass-crystal transition and find application in electrical or optical memory cells. The action of light on the substance was affected by an argon ion laser (lambda equals 0.514 micrometer). A modulating system furnished light pulses 0.2 microseconds to several seconds long. The laser beam was focused on the film to produce a spot with an area S less than or equal to 20 micrometers squared. The effect of exposure was monitored by measuring the transmission for a probing light beam (lambda equals 0.63 micrometer) focused on the place of incidence of the primary beam which induced changes in the optical properties of the film. Additionally, the film was viewed with a transmission microscope. Crystallization caused a decrease in transmission, whereas amorphization led to an increase in the transmission of a preliminarily crystallized film. When the critical value of power W_c was achieved, a local destruction in the form of a 'hole' was observed in the film.

A new method based on a combination of pyrometer and integrating sphere is proposed, allowing an express registration of temporal dependences of temperature, T(t), reflectivity, R_lambda(t), and absorptivity, A_lambda(t), of heat-conducting samples, when heated by continuous wave laser radiation. Computer-controlled acquisition and processing of these signals gives a possibility to obtain temperature dependences R_lambda(T) and A_lambda(T). In addition, a processing recorded by this method T(t) signal at cyclic heating and cooling of the 'thermally thin' sample (when laser beam is chopped periodically) allows us to find a temperature dependence of heat capacity C_p(T). Thus both the A_lambda(T) and C_p(T) dependences have been obtained simultaneously during the same laser heating in the range of temperatures beginning from the initial (room) temperature up to melting point or even above for iron, steels and other alloys, when heated by cw Nd:YAG laser radiation with wavelength lambda equals 1064 nm in vacuum, air and inert gas atmosphere at heating rates in the range 10³ divided by 10⁴ K/s. Experimental set-up and the proposed experimental technique are described. An analytical estimation of laser overheating of front surface compared with rear surface of the sample is given to prove a validity of the proposed method of heat capacity measurement.

Thin amorphous C-N films were deposited on <100> Si and KBr substrates at room temperature by XeCl laser ablation of graphite in low pressure (0.01 - 2.5 mbar) nitrogen atmosphere. Laser fluences were 3, 6, and 12 J/cm². Scanning electron microscopy, energy dispersion spectroscopy, x-ray diffraction spectroscopy, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy were used to characterize the deposited films, which result homogeneous, hard, amorphous and present a high electrical resistivity. The deposition rate decreases with increasing ambient pressure. The N/C atomic ratio into the deposited films generally increases with increasing ambient pressure and laser fluence. N/C values up to 0.5 were measured. Heating of the substrates during film deposition causes a reduction of the N/C ratio.

The interaction of subpicosecond laser pulses with metals is studied theoretically using phenomenological two-temperature model. Wide-range approximations for electron thermal conductivity and electron-ion energy exchange rate are proposed. Effects of temperature dependence of the thermophysical characteristics on lattice heating dynamics are discussed. Melting and evaporation kinetics are incorporated into the model to describe the metal ablation. Damage threshold and ablated layer thickness are calculated.

Pulsed, polarized UV-laser irradiation of polymers at 266 and 355 nm with Nd:YAG laser source gave rise not only to periodic structures of 100 nm dimension but also functional group alignments in periodic structures which were studied with a polarized reflected FT-IR spectrophotometer. The results arising from interference of scattered light on the surface and incoming polarized pulsed laser beams were demonstrated with poly(ethylene terephthalate), polyimides, polysulfones, polystyene and doped polyimides films. Images of polymer periodic structures were transferred to silicon surfaces by series of reactive ion etchings. Si patterns with 100 nm line and spacing with vertical wall profile were fabricated in a large area. On such Si surfaces diamond crystals were deposited from polymer plumes generated by ArF excimer laser irradiated in 193 nm on poly(methyl methacrylate). The diamond crystals deposited in this way have a very sharp Raman peak at 1332.9 cm^-1 with FWHM equals 1.2 cm^-1 to 14 cm^-1 depending on location on the substrate Si wafer.

In this work we report on a study of the plasma produced in laser ablation of aluminum targets by visible (532 nm) and UV (355 nm) radiation. In particular, we have obtained ion energy distributions through time-of-flight measurements in the laser ablation plasma at different laser fluences (3 - 60 Jcm^-2). The experimental TOF distributions of ions were fitted quite well by theoretical Maxwell-Boltzmann distributions superimposed onto a common center-of-mass flow velocity. By these fits ion plasma temperature and flow velocity were inferred. We also studied the ion yield at different laser fluences, observing a saturation behavior above a specific incident laser fluence.

Single-shot laser ablation of polyimide has been investigated with UV Ar⁺-laser radiation (lambda approximately equals 302 nm) for pulse lengths between 140 ns and 5000 ns. The dependences of the ablation rate on laser pulse length and intensity were measured by means of an atomic force microscope (AFM). These data are compared with mass-loss measurements using a microbalance. The experimental data are analyzed by taking into account both mass losses related to volatile product species and real material ablation.

The expansion of the laser induced plasma during material processing of Cu, Au, Si, and Si₃N₄ with ultrashort laser pulses is investigated using streak photography and high speed photography using delayed 35 ps laser pulses. Pulses of a diode-pumped, modelocked Nd:YAG laser which are amplified by a regenerative amplifier having pulse durations of 35 ps and a maximal energy of 0.1 mJ are used. Experiments are performed using both the fundamental wavelength of 1064 nm and by frequency doubling the wavelength of 532 nm. The onset of plasma formation is during the leading edge of the pulse. The spatial expansion of the plasma corresponds to the self-similar motion of a spherical plane wave in a gas. Independent of the processed material in ambient atmosphere the energy content of the shock wave is about one fifth of the optical energy of the laser pulse.

The species yields and velocity distributions in the vacuum plume of laser ablated pirolitic graphite were studied in detail by the time-of-flight mass spectrometry methods. Integral mass deposition on the opposite substrate was also investigated by use of quartz microbalance. At laser energy density near 2 J/cm² high yield of evaporation of clusters C₇ - C₂₇ is revealed. It is substantially higher in the case of preliminary ground graphite as compared with laser treated samples. First irradiation shots of a fresh graphite sample reveal the highest yield of C₇ - C₂₇ clusters and do not reveal a detectable number of fullerenes in the plume. Fullerenes are more abundant in the case of target rotation or laser spot displacement. Fullerene evaporation yield increases during a certain time period of laser ablation of moving graphite target. Two- stage character of fullerenes appearance in the plume is proposed. Firstly high mass clusters are formed in the plume tail -- the most cool part of the plume. As the pressure in the hot plume body is higher, most of the fullerenes formed deposit back on the target surface. Next laser pulses evaporate these clusters, which are stable enough to stand in the hot plume body. The C₇ - C₂₇ cluster ions are proposed to be mainly produced as a result of ejection of the pieces of graphite slices.

Irradiation of a solid target with a high power laser beam pressures in the matter up to tens and hundreds Mbar by the ablating plasma. The measurement of induced shock pressures is very useful and a sensitive parameter for optimizing compression in the inertial confinement fusion research for various experimental conditions (laser wavelength, pulse duration, etc.). On the other hand, such ultrahigh-pressure shock waves, which are not achievable in conventional laboratory experiments (flyer impact, explosive loads), have led to a strong interest in obtaining data measurements. Numerical simulation of laser-target interaction was conducted by many authors. One- and two-dimensional codes were used for these investigations. Because of the physical difficulty described phenomena it was used the different physical models with much simplicity proposition. Full description of laser-matter interaction must include such problems as: laser energy absorption, transport of the irradiated energy and subsequent ablation of the target; interaction of the ablated plasma with the ambient gas and formation of a shock and rarefaction waves; dependence of the energy absorption on the angle incidence and polarization of the laser pulse; instability fimbriation and evolution; fluency of the electromagnetic fields on the ablated plasma motion, both the early equilibrium and later nonequilibrium chemistry processes; electron-lattice relaxation phenomenon; irradiation of the plasma in the ambient gas, and so on. Metal (aluminum) targets with thickness 250 nm were used. Parameters of the laser pulse varies in range: intensity I equals 10¹³ - 10¹⁵ W/cm², duration varies in the range from 30 fs to 200 fs, wavelength lambda equals 0.35 mkm. The investigation has been performed by the 2-D Godunov's numerical scheme.

High quality ZnO, AlN, PZT thin films were deposited on different substrates (Si, sapphire, Corning glass) by reactive pulsed laser deposition technique using a Nd-YAG laser (lambda equals 1.06 micrometer, t_FWHM equals 10 ns, 0.3 J/pulse) as laser source. The depositions were performed in a stainless steel vacuum chamber (base pressure less than 10^-6 mbar) as follows: (1) Zn and PZT targets in high purity oxygen atmosphere, (2) Al target in ultrahigh purity nitrogen reactive atmosphere. Low collector temperatures (in the range of 0 - 350 degrees Celsius), high distance target collector (4 - 7 cm), high laser intensities, reactive gas pressure in the range of 10^-3 - 10^-1 mbar were found to be mandatory requirements for obtaining uniform, appropriate crystalline orientation thin films, with thickness in the range of 2 - 4 micrometer. Typical analysis as: x-ray diffraction, cross section SEM, x-ray photoelectron spectroscopy (XPS), Fourier transmission infrared spectroscopy (FTIR), secondary ion mass spectroscopy (SIMS), optical absorption spectroscopy were used to characterize the deposited films. They evidence the stoichiometric composition, crystalline structure with the c-axis perpendicular to substrate surface, columnar structure, etc. For the piezoelectric properties studies special structures were prepared: substrate (Si, etc.)/Cr(100 angstrom)/Au(1000 angstrom)/ZnO(or AlN, or PZT)/Al in order to configure an electroacoustic transducer for bulk acoustic wave generation and detection. The measurements confirm the good properties of the deposited films.

Interaction of nanosecond laser pulses with metal targets is investigated. Spall phenomena are studied for the pulse parameters: intensity varies in range I equals 10¹⁰ - 10¹² W/cm², pulse duration is order of 100 ns, wavelength is 1.06 mkm. These investigations were carried out both experimentally and with the help of numerical simulation.

Time-integrated optical emission spectra were recorded during XeCl laser ablation of graphite targets in vacuo and in low pressure (up to 2.5 mbar) N₂ and NH₃ atmospheres. The emission spectra of the laser induced plasma plume recorded during ablation in vacuo are dominated by the bands of the C₂ Swan system. Weaker bands from CN are well evident. Spectra recorded during ablation in NH₃ are also dominated by the bands of the C₂ Swan system. During ablation in N₂ (10^-4 - 2.5 mbar), strong bands of the CN violet system are detected. Their intensities increase with increasing N₂ pressure and with increasing distance from the graphite target. Mass spectra were recorded during ablation in vacuo (10^-6 mbar) and in N₂ at 1 multiplied by 10^-4 mbar. In vacuo, during the first stage of ablation, the mass spectra are characterized by the peaks at 12 and 26 a.m.u. (C and CN). The CN peak intensity decreases with the laser pulse number, to disappear after approximately 3000 laser pulses. In contrast, the peak at 26 a.m.u. is permanent during the whole ablation when N₂ is introduced in the chamber.

Ablation and condensation of film target under conditions of close-to-target substrate are considered. Different mechanisms of before-threshold film tearing-off from the donor substrate are examined. There is investigated the evaporative regime of the front transfer; thermal, gas- dynamical and hydrodynamical aspects of the process are considered. Investigations of the back transfer showed limitation of the deposited layer thickness in the multipulse regime. The maximum condensate thickness is defined.

During the first stage the layer melted by laser radiation is very thin. Under these conditions the motion is along the layer and this motion begins to change to cellular only when the heating effect reaches a threshold value. Therefore, the molten zone spreads rapidly until its size along the sample becomes approximately 40 times greater than in the direction of depth. The shape of the surface corresponds to that of shallow crater. However, the increase in the depth and surface area stimulates the stabilizing action of the thermocapillary effect. We shall calculate the layer thickness and the characteristics of convective motion under the simultaneous action of all the factors mentioned above. The problem is self-consistent since the film thickness and the characteristics of convection depend on one another. A detailed analysis of the results give us the mechanism of the formation of a zone which is melted by laser radiation.

The influence of titanium and lead dopants on the waveguide fabrication by ion exchange process and photoinduced second harmonic generation has been investigated. The similar effect of the glass composition on photoinduced second order nonlinearity and refractive index increment by ion exchange has been observed. The obtained results made it possible to rule out the influence of the glass structure on the charge transfer processes in lead silicate glasses.

We report the oxidation of different metallic surfaces (V, Co, Ta, W, Pt) under influence of multipulse excimer (XeCl) laser irradiation in atmospheric air environment. Thick (approximately 0.2 - 10 micrometer) oxide layers have been grown after a few hundreds of laser pulses at the fluences of 1.2 J/cm². The temperature behavior of irradiated samples showed nonlinear-nonequilibrium characteristics of oxide formation especially at higher repetition rates (greater than 100) of irradiation.

The self-action of spherically symmetric structure of electromagnetic field in a homogeneous isotropic Kerr-like medium is considered. Under certain conditions the induced spherically symmetric radially gradient distribution of refractive index acts as a microresonator, in which the effect of total internal reflection provides the existence of local spherically symmetric modes, that can be named structural resonances. The conditions of self-localization of three-dimensional spherically symmetric soliton are discussed.

The high-power laser beam interaction with the surface of metals (W, Fe, Ti, stainless steel) has been studied under high external pressures of the inert (Ar) and active (O₂) gases. The velocities of punching the samples have been measured at laser pulse power densities I equals 0.5 multiplied by 10⁶ - 10⁷ W/cm² in the beam revealed in punching velocities depending on the type of external gas. The dynamics of variations in the shape of high-power laser pulse reflected from the surface (W, Fe, Ti) has been studied.

The influence of self-organization processes upon character of a track induced by thermal action of scanning short-pulse laser radiation on metals is analyzed.

When heated, liquid semiconductors (semimetals) are subjected to a thermoelectric force. This force, along the usually considered buoyancy forces and the surface tension (thermo-capillary forces), can cause an instability. The thermoelectric force can generate cellular motion in a layer of liquid semiconductor not only when the heating is from below, but also when the heating is from above, where the excitation of different forces is not possible. The action of thermoelectricity is most intense in thin layers. Attention is drawn to the establishment of conditions for the excitation of convective thermoelectricity and the effect of thermoelectricity on the conditions for excitation by well-known, previously studied forces. Curves of neutral stability are presented, from which one can assess the contributions of each effect to the conditions of excitation. Particular attention is paid to elucidating the possibility of motion observed in experiments on the distribution of a liquid semiconductor (semimetal) by laser radiation. It is shown that including the thermoelectric effect permits an explanation for the presence of convection in a melted region subject to heating from above. The ratio of longitudinal and transverse dimensions of this region is found to be close to the aspect ratio observed experimentally.

Observation of self-induced oscillations of the light angular spectrum in a resonantly absorbing dichroic azobenzene dye doped nematic liquid crystal and magnetic liquid is reported. The nonlinear behavior is mainly caused by the superposition of thermal and orientational mechanisms of interaction. Self-induced asymmetry of the light angular spectrum due to the convective shift of an anisotropic nonlinear lens is observed as well.

The possibilities for an optimization of the reversible writing of holographic information in the organic photoconductor-liquid crystal system have been investigated synchronizing a supply voltage, the writing and readout regimes, as well as varying boundary conditions at the interface.

There is investigated the hydrodynamical flow of the glass at its surface acted by the laser scanning beam. Alterations of the glass viscosity and surface tension by local surface heating are taken into account. Stationary flow regime conditions, by which the crest of the softening material follows the irradiated zone with the same velocity and glass surface becomes smooth, are defined. The cases of the point and extended sources are considered.

Recently, several groups have demonstrated that the spatial and temporal temperature distribution inside metals resulting from femtosecond laser pulses cannot be fully explained by the two-temperature model for the electrons and phonons. Since these short pulse lengths may be comparable to the electron temperature relaxation time, we introduce a heat flow which is nonlocal in time. By this way we are taking into account in first order a non-equilibrium distribution of the electrons. As a consequence, three additional terms appear in the differential equation for the electron temperature. Furthermore, we offer an explanation for the different response of metals to the laser radiation on the basis of the electron-phonon coupling constant and the average phonon frequencies squared, well-known quantities in McMillan's theory on superconductivity. Using a double temperature model with nonlocal heat flow and a laser pulse length of 1 ps, the calculated surface temperatures of the electron and phonon subsystems are presented for Cu, Nb, and Pb. This is compared with the results of a local heat flow approach and with the conventional theory as well. Additionally we present calculations of the electron surface temperature of a thin Au film. We find that our model is capable of describing the new measurements on Au films more consistently than the standard double temperature model.

The interaction of an intense (10¹⁵ less than I less than 10¹⁷ W/cm²) subpicosecond (0.1 less than t less than 0.5 ps) normally incident laser pulses with solid targets is investigated. Target material heating, redistribution of the absorbed energy in the target, plasma creation and shock wave generation are investigated.

Presented work deals with the emission of the plasma heated by ultra-short intense laser pulses and the influence of the radiative heat transfer on the energy redistribution in the heated plasma with help numerical simulation. It was obtained the emitted photons spectra.

In the present work a new phenomenological approach to the accounting for relaxation near the phase transition temperature of the order-disorder type ferroelectric have been proposed. This approach is presented in the framework of pseudospin formalism and is based on the analogies with like those accounting for in para- and ferromagnetics. A relation between phase relaxation time of the critical vibrations, frequency of tunneling oscillations and the average constant of dipole-dipole interactions (or phase transition temperature) is found. This relation was obtained by use of mean field approximation. From differential equations for pseudospin components the Landau-Khalatnikov like equation for macroscopic ferroelectric polarization has been obtained. Self-consistence investigation of the last non-linear equation and Maxwell's equations is carried out in the low-frequency nonresonant regime. It is shown that in paraphase the dynamics of picosecond electromagnetic perturbations yields to the modified Korteweg-de Vries- Burgers equation. At the same time in ferroelectric phase these perturbations are described by the Korteweg-de Vries- Burgers equation. It is shown that electromagnetic shock wave and autowave formation near phase transition temperature is possible.

A stochastic model of ultra-short pulses interaction with a medium is based on simply the physical picture of matter and radiation, i.e., the matter as an ensemble of free electrons in the potential of ion lattice and radiation as a Poisson stream of laser light photons. In this model the basic reason of laser radiation absorption is collisional absorption of electrons. The iteration equation for photon stream intensity alteration after interaction with a single electron is obtained. Analysis of the suggested stochastic model permits us to find out criterion of pulse duration. According to this criterion ultra-short pulse is a pulse that does not change the medium's parameters (temperature, density, concentration of electrons, etc.) for a time of pulse duration. This definition is true for pulses, which have pulse duration less than the time of collision of electrons with ions, i.e. femtosecond and shorter pulses. It is shown that the main pulse parameter which determines the depth of laser penetration is pulse intensity. The pulse duration is a very important parameter, but its influence is not direct. The pulses of greater duration change media parameters for a time of pulse duration that leads to diminishing of the depth of laser penetration. For the laser light intensity is intratomic intensity or more in conductive media for laser frequency below plasma frequency the depth of laser penetration may arrive a few centimeters. For less intensity, the law of intensity attenuation is the well-known Bouguer-Lambert law. This proves possibility and adequacy of using the stochastic model of process of ultra short pulses interaction with a medium.