We describe the basic principles underlying resonant nonlinear magneto-optical spectroscopy of alkali atoms and show how the technique can be applied for high resolution investigations of weak and strongly suppressed processes in spin coherent atomic ensembles. We illustrate this by a detailed discussion of four distinct applications, viz. the detection of small biomagnetic fields, the space and time resolved tomographic study of gas phase diffusion, the measurement of linear and quadratic Stark effects in atomic ground states and the study of (quantum) crystal field effects on solid helium-isolated atomic defect structures.

The interaction between Rydberg systems [Rydberg atoms (RA) gas or Rydberg matter (RM)] and coherent light in various frequency bands is considered. It is shown why Rydberg systems possess a greater polarizabilities and, accordingly, linear and nonlinear susceptibilities and strong sensitive to high-1 (circular) Rydberg states in RA and RM. Quantum theory of physical and chemical properties of RA and RM are related with recent obtained results on the optical spectroscopy. The experimental data of Raman processes, wave mixing effects in gas of RA, and their clusters of RM are analyzed. Problem of blueshifts and stimulated electronic laser Raman processes, as well as four wave mixing in RM are discussed.

The self-consistent set of equations that describes the interaction of an atom with the electromagnetic field is proposed. The set includes the equations for vector and scalar potentials of electromagnetic field vector A(vector r,t), (phi) (vector r,t) and electron current and charge density vector j(vector r,t), (rho) (vector r,t). The obtained equations are similar to the magnetic hydrodynamics equation and differ from them by the presence of the terms depending on the logarithmic gradient of charge density. The specific feature of the obtained equations is that the steady-state distribution of the electron charge and current density is determined by the real and imaginary parts of the Schorodinger equation. The obtained equations are generalized for the relativistic case. In the latter case the equations include the atomic variables of the two types. The atomic variables of the first type are the bilinear forms of the wave function and Dirac conjugated wave function. The atomic variables of second type are the Hermitian conjugated combinations of the wave function first derivative and the Dirac conjugated wave function. Another specific feature of the obtained equations is that the equation for the electron current density can be transformed to the classical Hamilton-Jacobi equation with the new Hamiltonian. The phase of the wave function plays the role of action and new Hamiltonian includes the term depending on the logarithmic gradient of the electron density and its divergence. The relativistic Hamilton-Jacobi equation includes the term depending on the electron spin as well as the terms depending on electron density logarithmic four- gradient and its four-dimensional derivative.

An atom interacting with a quantized electromagnetic field in a cavity with time-dependent parameters is considered. Variation of the cavity parameters results in excitation of the atom, even if photons were initially absent in the cavity. We study a new mechanism of atom excitation and photon creation inside the cavity which we call the dynamical Lamb effect, and which has no relation to the dynamical Casimier effect. Several aspects of this mechanism are studied, including physical interpretation, amplification of the amplitude in the case of long-time periodic variation of the cavity parameters, and possible physical realization. Although the consideration is based mainly on a simple model of an atom interacting with a single mode of quantized electromagnetic field, and the results are qualitatively valid for more realistic models.

Experimental and theoretical investigation of the coherent propagation and amplification of polychromatic broadband laser pulses in optically dense resonant media without population inversion was carried out for the cases of plasma in a Ne glow discharge and a pulse discharge in Hg-Ar mixture. High density of Ne and Hg atoms in the metastable state (about 10¹² cm^-3), which was chosen to be the ground state of the two-level system under consideration, leads to the collective behavior of the atomic system in resonant electromagnetic field. The broadband probe field attenuation and the sideband amplification of the probe under the action of the coherent pump were observed. The amplification dependence on the pump intensity was obtained. The model of the parametrically enhanced collective interactions was developed and comparison the experimental data was made.

An efficient broadband optical continua generation due to stimulated Raman scattering originated from relaxation processes from the excited electronic states is predicted. It is shown that, even when the populations of Raman levels are equal, Raman coherence can be efficiently excited due to coherent population trapping process (CPT). Scattering of the electromagnetic field due to the excited coherence gives rise to a comb of equally spaced spectral components of optical radiation. The generated spectrum can be compressed into a sequence of ultrashort pulses. Estimates for realistic parameters of the medium show that it is possible to produce a sequence of femtosecond and even subfemtosecond pulses with repetition rate several GHz.

Coherent transient phenomena can be generated by the abrupt changes of parameters either of the electromagnetic field or of the matter. Comparative analysis of these two approaches, made on the base of experimental research in molecular gases SF₆, ¹⁵NH₃, HFCO and ¹³CH₃F, excited by the radiation of CW CO₂ and ¹³CO₂ lasers, is presented. The first approach of photon echo (and its modifications) generation, based on electro-optic pulses formation from the resonant CW exciting radiation, has proven to be successful for intense infrared molecular transitions. The coherent responses are sufficiently powerful to be applied in high resolution spectroscopy, the spectral markers creation ,and molecular collisions investigations. However, this technique is not very effective for the free polarization decay investigations. Another approach based on the Stark switching molecular levels of polar gas, irradiated by CW laser, was demonstrated for free polarization decay and photon echo generation in ¹³CH₃F. Free polarization decay has shown the pronounced frequency shift because of dynamic Stark effect in the CW radiation field. This specific feature of coherent transients, created by Stark switching, limits the high resolution spectroscopy by the low intensity range of exciting radiation. From other viewpoint, it gives unique possibility to investigate coherent transients generated at the dressed molecular levels.

We present analytical and invariant expressions for the steady-state density matrix of atoms in a resonant radiation field with arbitrary intensity and arbitrary elliptical polarization. The field drives the closed dipole transition with arbitrary values of the angular momenta of the ground J_g and excited J_e states. These transitions can be classified depending on the structure of the solution and its physical peculiarities.

The possibility of realization of a spherically symmetric structure of electromagnetic field in a homogeneous isotropic medium is analyzed. The existence of this spherical structure is determined by a radial-gradient distribution of the nonlinear refractive index, which acts as a spherical microcavity induced in the nonlinear medium. Mechanisms and conditions of self-organization of the spherically symmetric structural resonance are discussed on a basis of the nonlinear-optical and quantum-mechanical approaches. Dynamics and stability of the structural resonance in the nonlinear medium are considered.

A model for multiple photon excitation of molecular vibrational modes by an infrared laser field is developed. The closed semiclassical Heisenberg equations of motion for a periodically driven anharmonic oscillator with two degrees of freedom are derived. The equations for a free nonlinear oscillator with two degrees of freedom are shown to be integrable with solution in terms of Jacobian elliptic functions resulting in a strictly regular intermode exchange of energy. When illuminating the molecule by a periodic infrared laser field, the absorption may strongly depend on the values of the molecular and laser parameters. We find numerically that the molecule may absorb coherent laser light chaotically. A mechanism of the onset of Hamiltonian chaos in our system is studied, using Poincare sections.

The characteristic peculiarities of the self-reflection of a strong electromagnetic wave in a system of coherent excitons and biexcitons due to the exciton-photon interaction and optical exciton-biexciton conversion in semiconductors were investigated as one of the manifestations of nonlinear optical Stark-effect. It was found that a monotonously decreasing standing wave with an exponential decreasing spatial tail is formed in the semiconductor. Under the action of the field of a strong pulse, an optically homogeneous medium is converted, into the medium with distributed feedback. The appearance of the spatially separated narrow pears of the reflective index, extinction and reflection coefficients is predicted.

Free polarization decay and photon echo were studied experimentally in polar gas ¹³CH₃F at the transition R(4,3) of vibrational mode 0 yields 1 (nu) ₃ by Stark switching of molecular levels under irradiation by CW CO₂ laser at 9P(32) line. Application of 4.5 mcs pulse to the Stark electrodes inside the gas cell allows to detect the free polarization decay signal, combined with the optical nutation. The sign of the signal corresponds to the increase of absorption in the limit of low intensity (not over 0.01 W/cm²) saturating radiation. Exciting intensity growth till the level of 6.0 W/cm² implies decrease of signal absolute value, till the change of its sign, while the oscillation of the free polarization decay signal reveals remarkable frequency shift. Such behavior is attributed to the combined action of the dynamic Stark effect of CW radiation field and the levels splitting by the Stark voltage. Two shorter (of about 0.1 and 0.2 mcs) Stark pulses, applied to the gas, generate the photon echo signals detected by the same heterodyne technique. The study of the variations of photon echo parameters versus exciting radiation intensity is in progress.

Lasing on the sodium resonance transitions (D₁ and D₂ lines) at the superluminosity regime was observed upon the nonresonance excitation in the presence of a buffer gas. Dependences of the lasing intensity on the pump radiation intensity and its frequency detuning from the frequencies of resonance transitions were examined. It was found that under the specific experimental conditions (high buffer gas pressure, sufficiently high intensity of pump radiation) upon the large positive frequency detuning of pump radiation with respect to the frequency of resonance (working) transition, contrary to ingrained conceptions, population inversion for the working transition is raised. That results in observed phenomena.

In this paper we report both experimental and theoretical results on Rayleigh-Benard and Marangoni convection instability experiments in isotropic liquids and nematic liquid crystals. This instability is driven and controlled by medium absorbing a light radiation with a spatially periodical transverse structure. This instability has rather thermal than hydrodynamic nature because Prandtl number is much larger than one for our media. We study the competition of two mechanisms for reorientation of the liquid crystal molecules. Gravitational and thermocapillary hydrodynamic waves induced by traveling spatially periodical distribution of light intensity are observed and investigated. The stability of these waves is studied as well. We also study the influence of convective motions on the isotropic liquid- liquid crystal phase transition.

A novel method of resonant absorption suppression of monochromatic radiation via supersonic mechanical vibration of medium sample along radiation propagation is proposed. Steady-state field propagation without resonant absorption and appearance of spectral components is predicted.

Polarizability difference at the states, forming Raman- active transition is found to be a good characteristic of a molecule properties with respect to the Raman scattering of light. Stimulated Raman gain and spontaneous Raman scattering cross-section are calculated through the polarizability difference. Estimates have been done for hydrogen molecule.

Spontaneous coherence transfer has been studied experimentally using two-color laser polarization spectroscopy of ⁸⁷Rb. Two classes of optical transitions were investigated for which the theory predicts presence and absence of anisotropy of a hyperfine sublevel of the ground state populated via spontaneous decay. The anisotropy was induced by a strong linearly polarized laser beam. It was controlled by the polarization rotation of another probe laser beam. A qualitative agreement with the theoretical predictions has been found.

The transmission of sequence with ultrashort light pulses through the resonant cavity structure are considered. The features of the Photon Echoes effect are researched. It is shown that the dynamic efficiency in a holographic formation of nonstationary images can substantially exceed the analogous quantity in the case of bulk excitation of the resonant medium.

It was shown experimentally, that in elastic soft polymer samples such as rubber the IR-laser pulse excites components of the soliton-like Wave of change of reflection and conduction (WCRC). It is most probable, that the arrival of a wave results in local decreasing of the temperature of different rubber samples. At room temperature the WCRC velocity measurement for two vacuum rubber samples with different thickness given agreeable data correspond to the nineteenth WCRC component. In crude, not polymerized rubber and at cooling of vacuum rubber up to approximately 230 K the WCRC also was excited. As well as in researches with plexiglas, in the present work of the effect of saturation of a new sample by components of soliton-like WCRC was observed. The obtained data confirm availability of soliton properties for studied WCRC and in applicability of the dislocations recombination mechanism as the causes resulting in formation WCRC. These results are important for the WCRC mechanism development. It presents a phenomenon, which in process of its research appears to be more and more universal. The work was made at financial support by RFBR, project 00-02-17249-(a), and by KIE.

It has been first established that the optical pumping of cesium vapor by pulse dye laser, tunable within the range 17020 cm¹ - 19200 CM^-1 and 20150 cm^-1 - 21390 cm^-1, lead to the powerful stimulated IR radiation on several atomic transitions. The mechanism of this phenomenon has been suggested.

Local spectral density (LSD) of quasienergies is investigated for a generic system of coupled quantum states represented by a superimposed band random matrix with preferential basis. The shape, the inverse participation ratio and the localization regimes for LSD are studied under conditions when the states are isolated or excited by a field, the shape of which is close to monochromatic one.

Transient processes are analyzed based on modified Bloch equations describing the interaction of optical radiation with dense resonant media with allowance for dipole-dipole interaction between atoms (the local-field effect). An analytical solution to the equation for the population difference of resonant atomic levels, taking into account the up-conversion processes, is obtained for a rectangular pulse in the quasi-stationary approximation. Computer simulation is performed for the kinetics of the population difference of resonant atomic levels in the field of a long sine-shaped pulse. It is shown that the time dynamics of the population difference of resonant atomic levels manifests characteristic features inherent in the intrinsic optical bistability effect under adiabatically slow variation of the acting field.

Experimental studies of the laser-induced Al plasma expansion during laser pulse into ambient air under pressures of 76 - 760 Torr was performed using 2-channel ADC attached to photomultipliers. Simultaneous measurements of the temporal dynamics of entire plasma emission and neutral Al 396.15 nm emission vs. laser pulse form were carried out with resolution 10 ns. It was detected dualization of a plasma head front, corresponding laser Q-switched pulse. This phenomena may be caused by decay of the laser-supported detonation wave. Distance on which plasma front observed vs. time was obtained under different pump energy of Nd:YAG laser. These results show that plasma expansion dynamics can be described by fast ionization wave model and laser- supported detonation wave model depending on laser pulse form.

The present paper is devoted to the introduction of enhanced model describing an interaction between laser radiation and dielectric medium. This model is based on our earlier researches, and contains a correct description of the dispersion of electrical field's third order nonlinear medium polarization response in a wide spectral range. We have accomplished this description by a pseudo-classical model of multi-photon ionization of optical medium particles (structural elements). A wave equation, describing wide- spectrum femtosecond pulse propagation in nonlinear medium with induced plasma non-linearity, is obtained.

We present a theoretical model and results of the detailed numerical investigation of peculiarities accompanying the interaction of powerful sub-picosecond light pulses with a bulk dielectric sample.

Rubidium vapor (10¹¹ - 10¹⁴ cm^-3) was irradiated by a dye-laser beam (10 kW(DOT)cm^-2 - 2 MW(DOT)cm^-2, pulse duration approximately 30 nsec, linewidth <EQ 0.25 cm^-1), which was tuned to the D_1,2-resonance lines. The mutual competition of the two photon ionization, associative ionization and Penning ionization of the laser excited rubidium atoms was investigated. The data of laser intensities and a rubidium vapor concentrations, which results in domination of the each ionization channels were founded. On the basis of the received experimental results, the cross-section values for the multiphoton and collisional ionization channels of laser-excited atoms were determined.

The optical characteristics of a medium with cylindrical pores are investigated theoretically by using the effective refractive index which is found from the dispersion equation for an infinite medium. In frame of quasi-crystal approximation the dispersion equations are obtained for the wave vector of a coherent electromagnetic wave propagating in a media which contains a random set of parallel overlapping cylinders. It is shown that the spectral characteristics of porous medium depend on the regularity in pores placement.

The theory of cascade lines generation by means of stimulated Raman scattering in molecular and atomic gases is developed. The specific features of generated spectra are analyzed. The possibilities of fs pulses generation are suggested.

We demonstrate that quasi-steady states for a highly excited atom in the vicinity of ionization threshold in a strong self-consistent oscillating magnetic field can be represented in the form of an expansion on coherent states of a Dirac electron moving in self-consistent atomic potential. The asymptotic solutions have been constructed based on the perturbation theory.

Microwave Hanle effect has been studied in sodium Rydberg atoms for the first time. Spontaneous emission of the microwave transition 37P_3/2 yields 37S_1/2 at 70.166 GHz was replaced by an induced transition from a pulsed microwave source. Good agreement with the theoretical calculations has been found. The widths and shapes of observed resonances were defined by the spectral widths of the pulsed microwave radiation and parameters of laser excitation of the initial 37P_3/2 state. The interference occurred in the scheme of transitions similar to the Mach- Zehnder optical interferometer.

Prospects of charge-transfer pumping of laser-produced ions are discussed. The results of numerical simulation of the problem are presented. By means of laser-produced plasma a selective population of O⁺⁵ ion following a charge transfer interaction O⁺⁶+H₂ is studied. A distribution among the sublevels s, p, d, f of the most preferably populated 4 level is measured for the first time at relatively low colliding velocities approximately 2 (DOT) 10⁷ cm/s.

Only recently a rigid quantum-mechanical modeling of free- electron induced optical nonlinearities in highly doped n- GaAs has been elaborated. The total theory takes into account non-parabolicity, hot phonons, effective mass modulation due to (Gamma) -L intervalley transfers, scattering due to equivalent intervalley transfers inside the ellipsoidal L-valleys, nonlinear screening, etc. It was shown that this hot free electron nonlinearity is strongest near the plasma resonance and significantly depends on the deformation potential field (Lambda) _LL describing transitions of L-valley electrons between equivalent L- minima. For the experiments a very sensitive multi-layer leaky waveguide structure for TM polarized waves was designed and grown by MBE. Measurements were performed with 100 ns duration CO₂ laser pulses. For a doping concentration n_o of 7.6 X 10¹⁸cm^-3 a nonlinear refractive index value n₂ equals (1.0 + 0.12)X10^-6 cm²W^-1 at (lambda) equals 10.6 micrometers was obtained, which was based on an experimentally derived (Lambda) _LL equals (1.0 +/- 0.2) X 10⁹ eVcm^-1. With intensities of only several MWcm^-2 more than 50% of the electrons cold be transferred to the L-valleys, leading to impressive absorption increases of more than 50%. With respect to bulk samples the nonlinearity could be more than 20 times increased. In combination with an estimated relaxation time of 6 - 7 ps, this nonlinearity exceeds most other results at room temperature for (lambda) equals 10.6micrometers .

The generalized theory of the Hanle effect is developed for the case of propagation quantum beats. Time-integrated quantum beats of two polariton wave packets with the same group velocities and polarizations belonging to two different Zeeman components in Voigt geometry of the quadrupole-active ortho-exciton (Gamma) ₅⁺ level in Cu₂O crystal gives rise to the propagation Hanle effect. It is characterized by a quasiresonant dependence of the emitted light intensity on the magnetic field strength, as well as by a supplementary periodic dependence with the period inverse proportional to the sample thickness. The developed theory with the account of the effective propagation way explains recent experimental results published by Kono and Nagasawa.

Based on the investigation of the temperature dependence of the two-pulse phonon echo amplitude on the ³H₄ ³P_o resonant optical transition of the Pr³⁺ doped ions in the Y₂SiO₅ crystal, unusual for crystals, low-temperature mechanisms of Pr³⁺ spectral line broadening caused by the interaction of doped ions with TLS have been found. The constants characterizing the interaction of the doped Pr³⁺ ions with phonons and TLS have been determined.

The numerical model for description of interaction of ionizing and UV laser radiation with CaF₂ is submitted. Is shown, that the appearance of short-lived electronic excitations in a crystal strongly affects on nonlinear absorption of laser radiation at pulse duration more than 0.1 ns. The consequences of this absorption for structure of crystal are analyzed.

Lithium niobate is a perspective material for recording of the polarization-phase holograms in the optical systems of information processing and storage. In this work, the direct and back photorefraction scattering in LiNbO₃ crystals with iron and rhodium as alloying additives have been studied. When comparing the photorefraction scattering in LiNbO₃:Rh and LiNbO₃:Fe it was established that a kind of additive has influence on both quantitative characteristics of the photorefraction scattering in lithium niobate and on its nature. The selective component in back scattering in LiNbO₃:Fe has been found.

A theoretical treatment of the resonant hyper-Raman scattering (RHRS) of light by 2LO-phonons is presented for a CdS crystal. The scattering mechanisms of the RHRS by 1LO- and 2LO-phonons are considered. The corresponding efficiencies are compared.

The theory of solitons of new type is developed: the fast and slow deformation-thermal (DT) solitons, excited by laser pulse action on the surface of strongly absorbing solid plates and films and propagating into the bulk. The comparison of theoretical and experimental results is carried out.

Resonant effect connected with nonlinear light propagation through dielectric with small non-absorbing microinclusion is considered. It can play important role in initiating of laser-induced damage of transparent materials through local increasing of laser intensity inside and near the microinclusion. The effect is developing of field instability in nonabsorbing microinclusions resulting from excitation of resonant mode through inducing of variations of refractive index. It is shown that transparent microinclusion can initiate about 10 times local increase of laser intensity accompanied by positive feedback. If the electric field strength exceeds damage threshold during nonlinear evolution in the inclusion then developing of field instability results in damage of micro-inclusion before electric field is stabilized at certain upper level determined by ionization processes. There estimated threshold of field instability is about several MV/cm. Its dependence on material and radiation parameters is studied.

Generalized Semiconductor Bloch Equations are derived with using the fluctuation-dissipation theorem. Four operator expectation values like density-density correlators are calculated with account of coherent memory effects. Interactions with mixed plasmon-phonons modes and excitonic effects are taken into account. Comparison with different other theoretical approaches is provided. Numerical calculations of the spontaneous radiation produced by interband multiplasmon recombination of electron-hole pairs are fulfilled in dependence on the temperature and plasma concentration. It is shown that the intensity maximum of spontaneous radiation shifted to the region of the first LO- phonon satellite with increasing of concentration in accordance with experiments.

An approach to calculation of nonlinear susceptibilities of semiconductors in far infrared and microwave range based on account of interaction of free carries with intrinsic excitations of semiconductors and ionized impurities is developed. Numerical dependencies of real part of third order non-linear susceptibility on frequency, temperature and concentration of impurities for a set of semiconductors are obtained.

In the paper there are presented the last results of computer simulations on the spectra of magneto-optical rotation (MOR) of plane of polarization for the both components of intense bichromatic laser radiation. Also the dependences of MOR on light intensity and magnetic field strength are investigated. The calculations are based on the theory and method, published earlier. The agreement of calculations for the cases investigated in the known experiments with experimental results permits to hope that new peculiarities of the MOR in alkaline vapors considered in our paper can be observed in the natural experiments.

The results of experimental and theoretical studies of the properties of holey fibers are presented. The fabrication of holey fibers with a pitch of the two-dimensional periodic structure of the cladding less than 500 nm allowed us to experimentally observe a photonic band gap in transmission spectra of holey fibers tunable within the range of 930 - 1030 nm. It is demonstrated that holey fibers provide an opportunity to considerably increase the efficiency of spectral broadening and phase control of short laser pulses as compared with conventional fibers.

A combination of a diffraction grating and a mirror integrates a hollow waveguide and a photonic band-gap structure into a compact optical element, offering a simple new structure for various applications in nonlinear and ultrafast optics. The main features of transmission spectra observed in experiments performed with such waveguide structures are qualitatively interpreted in terms of the coupled-mode theory. Localization of light near the surface of a metal-coated grating in lowest order TM modes in the created waveguide enhances effects related to the photonic band-gap structure.

The master equation for impurity atom in photonic band gap crystal is derived with account for two-atom and two-photon relaxation processes. Important role of these relaxation processes is clarified.

Electrochemically nanostructured Si films with surface orientation (110) prepared at different current density were investigated by Fourier transform infrared spectroscopy. The spectra exhibit beats of interference fringes arisen from the summation of intensities of ordinary and extraordinary waves which interfere in the film. The investigated films are shown to exhibit properties of a negative uniaxial crystal (n_o > n_e) with optical axis lying in the surface plane along [001] direction. The value of birefringence reaches 18% for nanostructured Si films with porosity of 80%. Experimental data agree with calculations based on the effective media approximation for anisotropically spaced Si nanocrystals.

The capabilities of one-dimensional photonic band-gap (PBG) structures to simultaneously phase-match several optical fields with different frequencies propagating in a dispersive medium are examined. A dispersion relation for an infinite one-dimensional PBG structure whose unit cell consists of three different materials is derived. Analysis of this dispersion relation shows that structures of this type provide additional degrees of freedom in dispersion control relative to conventional, binary one-dimensional PBG structures. In particular, the increase in the number of layers with different refractive indices in a unit cell of a PBG structure allows a larger number of optical fields with different frequencies to be simultaneously phase-matched. The possibilities of using this property of ternary PBG structures for synthesizing trains of subfemtosecond pulses are discussed.

The study of the linear, nonlinear, and photo-induced behavior in a magneto-optic micro-cavity in the strong coupling regime is investigated using the reflectivity and magneto-optic Kerr rotation techniques. The photo-induced modifications of the strong coupling regime are traced to the light induced changes of the exciton transition by many body interactions and band filling effects. At a fluence of 1 (mu) J/cm^-2 the saturation and blue shift of the quantum well exciton transition produce strong modifications of the lower polariton frequency which induce nonlinear magneto-optic Kerr rotations of 30 degrees at a magnetic field amplitude of 0.2 Tesla. With no applied magnetic field polarization rotations of more than 10 degrees are photo- induced by 1 (mu) J/cm^-2 fluence circularly polarized pump pulses. Such a physical effect could be interesting for high contrast fast optical signal processing when room temperature operation becomes available.

Intensity dependent transmission and excited state relaxation measurements of PbS and PbSe quantum dots in silicate and phosphate glasses and their applications for mode-locking of Nd:YAG laser at 1.064 micrometers as well as for Q-switching of Nd:KGW at 1.067 micrometers and 1.35 micrometers and Er:glass at 1.54 micrometers lasers with diode and flash-lamp pumping are presented.

This report presents the discovery of greatly enhanced, broad-range, multiphoton excited emission from Ag aggregate- adsorbate complexes seeded into a cylindrical microcavity. The emission spectrum contains descrete peaks spanning the wavelength range from the 632 nm HeNe laser exciting wavelength down to 200 nm. Observation of multiphoton processes at the low exciting light intensity (20 W/cm²) became possible due to using a fractal-microcavity composite, where coupling the localized plasmon modes in fractal aggregates with microcavity resonances is provided. The important role of the multiphoton resonant transitions between discrete states of a finite-size metal particle in enhanced local fields is shown. Analysis, based on the model of a spherical potential well, shows that the observed spectra contain fingerprints of the quantum size effect.

The theory of nanoscale surface melting induced by long range screened defect-defect interactions is developed. The thickness of quasiliquid surface layer is shown to be an exponential function of temperature detuning from the melting point in accordance with the empirical dependence. Obtained results justify the modeling of observed strong nonlinear optical response of alpha-Ga films and single crystals below the melting point in terms of laser-induced nonthermal nanoscale surface melting.

Dipole-forbidden states of trans-nanopolyacetylene in the near infra-red are probed by a photothermal method at room temperature. We found that light absorption at approximately 1 micrometers is four orders weaker than that corresponding to the main dipole-allowed transition.

The interaction of an atomic group occupation a volume with linear dimensions which are considerably smaller than the length of an external light wave in considered. On the basis of the join set of equation for the electronic field strength of the light wave and the optical equation for linear dipole oscillators, the points of location of the atoms, as well as at different points of observation outside the atomic group (a small object) in the wave and near-field zones, is solved. We are predicted theoretically optical size resonances in atomic nanostructures on the basic a new solution for electric dipole moment. We presented here also experiments, where size resonances was observed and some applications of size resonances.

The effect of the Coulomb charging energy on the time evolution of the electron occupation probability in a coupled-quantum-dot system is investigated by use the nonlinear coupled equations, derived from the Schrodinger equation taking into account the Coulomb blockade of the resonant electron tunneling.

The light scattering from a nano-sized object formed by two or three dipole atoms (polarizable components) is studied in detail using a microscopic approach. The atoms are considered to be linear Lorenz oscillators interacting via the electromagnetic field only. For simple configuration of nano-object, the self-consistent electromagnetic problem is solved analytically. It is shown that the near-field interaction between the dipole atoms can give rise to a dramatic modification of the polarizing characteristics of atoms and the total polarizability of nano-object. We point out the existence of a number of resonance peaks in the frequency dependences. The shift of resonance peaks from the position of the resonances corresponding to the isolated atoms depends mainly on the interatomic distances and can significantly exceed the natural linewidth. Generally, the resonance characteristics of atoms depend on various system parameters such as the atomic polarizabilities (i.e. the eigenfrequencies), the number of atoms, and the interatomic distances. The scattered light intensity detected in wave zone is shown to depend essentially on the configuration of nano-object, the light frequency, polarization, and direction of external wave.

We measured small Faraday polarization rotation in nanopolyacetylene in a magnetic field approximately 150 Oe. We found that approximately 1% polyacetylene nanoparticles increase up to 50% the polarization rotation angle of the transparent matrix containing them when probed near and at the NPA absorption band. The rotation angles were in the range 1 - 15 (mu) rad.

Polarization and coherent effects for chain-ordered planar arrays of metallic nanospheres have been investigated within the framework of the model of binary interactions. The dependence of plasmon resonance frequency on the light polarization state due to the lateral electrodynamic coupling has been revealed. The effect of nanoparticle space ordering on the shape of the natural light absorption spectra have been established.

Dependence of the nonlinear refraction coefficient on light intensity in the GaAs-AlGaAs quantum-well heterostructures is established. Effects of spectral broadening and light polarization are taken into account in the calculations based on the Kramers-Kronig relation.

Optical properties of fractal Cantor-like multilayer nanostructures are investigated numerically and experimentally. Strong correlation between the stack geometry and the properties of optical transmission spectra is found, namely spectral scalability and sequential splitting. A good agreement is achieved between the experimentally measured and calculated spectra.

The influence of layer thickness, heterostructure design, optical confinement factor and spontaneous emission efficiency on laser parameters of GaN based quantum well optically pumped lasers is studied in wide spectral (373 - 470 nm), temperature (77 - 600 K) and excitation intensity (10² - 3 10⁶ W/cm²) regions. The laser threshold enhancement from 70 kW/cm² for the 421 nm operating laser to 900 kW/cm² for the 469.5 nm laser leads to the reduction of highest operation temperature of the laser from 585 K for the 421 nm laser to 295 K for the 469.5 nm laser with increasing operating wavelength. As a rule the far field pattern of the laser emission consists of two light spots localized at positive and negative angles of 30 - 50 degree(s). The laser spectra structure in the far-field of the SQWs and MQWs with low thickness of the active layers depended on the registration angle. The spatial distribution of the laser light in the far-field consisting of transverse and leaky modes was calculated and compared with the experimental results. Calculations of the optical confinement factor and the electromagnetic field distribution inside and outside of the heterostructures showed that the MQW lasers operate in the high order transverse mode regime. The spectral-angular distribution of the emission of the SQW and MQW lasers with low active layer thickness is due to the leaky mode formation.

Highly monodisperse CdSe quantum dots 1.8 nm in size were synthesized capped with surface monolayer of 1-thioglycerol. The optical absorption of thin films of matrix free close- packed and isolated in PMMA matrix quantum dots was studied at various electric field biases. The broadening and red shift of optical transitions in close-packed ensemble against isolated is attributed to the formation of collective electronic submini-bands between interacting nanocrystals. The reversible collapse of collective electronic subminibands has been achieved by applying of strong electric field to the thin film of close-packed quantum dots.

The optical characteristics (the diffuse reflection and transmission coefficients, direct transmission coefficient) of the aqueous suspensions of various ultra-disperse diamonds (UDD) modifications have been investigated at the single light scattering conditions coefficient at the range of 300 - 700 nm. The spectra of the absorption and scattering coefficients were calculated. Analysis of the obtained spectra of the absorption coefficients permits to identify the absorption bands because of presence of the different carbon forms (graphite, soot), haematite, etc. and to determine their quantitative contents. The sizes of UDD aggregates in aqueous suspensions were estimated by the using of the scattering coefficient spectra. Obtained results are evident on efficiency of the optical methods of application for assessment of the surface chemistry of the UDD.

With the use of Raman scattering spectroscopy and electron microscopy techniques it was observed that nanosecond pulse excimer laser radiation impacts lead to formation into a- Si:H films on not-orienting glass substrates nanocrystals with preferred (110) orientation and sizes from 2 nm and bigger. The dependence of average size and concentration of nanocrystals on parameters of laser impacts (energy density and number of shots) was studied. Polarization anisotropy of the Raman scattering was observed in the system of mutual- oriented silicon nanocrystals. The analysis of polarization dependence of Raman scattering intensity makes possible to determine the part of the oriented nanocrystals. It is proposed, that preferred orientation is due to both elastic stress in the films and local deformations appearing around the nanocrystals. Features of explosive crystallization during excimer laser impact were observed. This effect can be result of significant mechanical stresses in a-Si:H films on glass substrates.

The analytical and experimental investigations describing the intracavity processing of different solid-sate materials (Al, Cr, Ge, Si) are presented. New designs of the laser cavity were explored to facilitate the fabrication of structures composed of a system of equidistant parallel 250 nm-sized grooves and periodic micro-dots on massive samples of metals and semiconductors, as well as micro-holes in thin film metallic samples.

We report on the improvements of an InGaAs/InP quantum wire (QWR) laser leading to a new concept of a single QWR laser. Its index/gain guiding structure consists of a vertical waveguide in combination with a laterally patterned semi- insulating current blocking layer with an additional oxide layer, which is realized by a simple self-aligning sub-micrometers lithography step. A further improvement of the structure is possible by reducing the thickness of InP buffer layers, which were necessary due to technological reasons. One InP buffer layer may be omitted completely by increasing the growth temperature from 600 degree(s)C to 640 degree(s)C. By employing metal-organic vapor-phase epitaxy we found a significant increase of In-content of the QWRs at the raised temperature.