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A Kerr nonlinear medium consisting of an aqueous suspension of dielectric nanoparticles is used for the observation of continuous self-focusing of laser light. The minimum width of the soliton-like beam is measured in relation to the radiation power and the particle concentration. The possibilities of maximum narrowing of the beam in such a medium are discussed. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Semiempirical equations have been derived for determining the rate of slow hindered motion of spherical particles in a liquid, which agree with empirical data with a high degree of accuracy. It has been shown that the variational principle of the minimum intensity of energy dissipation can be used in determining the rate of hindered motion. [ABSTRACT FROM AUTHOR]

An expression is obtained for determining the dimensionless velocity in the processes of settling and fluidization for spherical, cylindrical, and cubic particles in a self-similar region. [ABSTRACT FROM AUTHOR]

A combination of variational and empirical methods to determine the porosity is used to give a theoretical explanation of the power-law dependence of the dimensionless velocity of the constrained motion of particles during sedimentation. [ABSTRACT FROM AUTHOR]

The method of calculating the electromagnetic wave field diffracted by a holographic grating with a multilayer dielectric coating is developed. The method consists of the representation of the field inside dielectric layers in the form of a plane-wave expansion for weakly damped harmonics and an expansion over functions of the concomitant coordinate system for strongly damped orders. This modification of the method allows calculation of the diffraction efficiency and the electric field strength for the deep groove gratings. It is shown that a diffraction element that possess high efficiency and radiation strength can be obtained even when the profile of the dielectric layers flattens with an increase in the distance from the grating’s metallic layer. [ABSTRACT FROM AUTHOR]

Equations are obtained for calculating the rate of onset of fluidization and the onset of complete fluidization, taking into account the dependence of the drag coefficients on the porosity in the region of preliminary expansion of the bed before complete fluidization. [ABSTRACT FROM AUTHOR]

A femtosecond laser based on an Yb:KYW crystal with direct longitudinal pumping by a high-power semiconductor injection laser with a fiber output is described. Femtosecond pulses were generated in the self-longitudinal-mode-locking operating condition due to the use of a semiconductor saturable absorber. The average power of the oscillator was as high as 3.5 W at a central wavelength of 1035 nm, the pulse length and pulse repetition rate being 200 fs and 85.5 MHz, respectively. The product of the pulse length and the radiation spectrum width was 1.3 times higher than the theoretical limit for the pulse shape described by the function sech2. The designed master oscillator can be also used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems. [ABSTRACT FROM AUTHOR]

The final stage of self-focusing of 500-ps pulses of a neodymium laser in silicate and phosphate glasses and in the nonlinear liquids perfluorooctane, benzene, and toluene is studied theoretically and experimentally. The formation of spatial solitons, which are stable due to the nonlinearity saturation, is demonstrated. It is found that the intensity of the nonlinearity saturation is close to that of the threshold breakdown for glasses and the role of stimulated Raman scattering is significant for liquids. [ABSTRACT FROM AUTHOR]

The diffraction efficiency and the resistance to radiation damage of gratings with a multilayer dielectric coating, which are used for compression of high-power laser pulses, are studied. The effect of smoothing of the profile of the metallized surface of the grating upon deposition of dielectric coatings on the energy characteristics of the grating at the wavelength λ = 1.05 μm is analyzed. Gratings with various profiles of the metallic surface relief and with different contrast of the refractive indices of the dielectrics forming the coating are considered. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Theoretical estimates are given along with the first experimental results on the observation of resonance fluorescence in nuclei of rubidium isomer under conditions of laser plasma X-ray pumping of the contiguous transition with an energy of 3.4 keV. The laser plasma is prepared by irradiating a silver target by a powerful radiation of a Nd laser with a pulse duration of 600 ps. It is demonstrated how one can use the recorded number of emitted γ quanta to determine the probability of low-energy nuclear transition excited by laser plasma X rays. [ABSTRACT FROM AUTHOR]

A repetitively pulsed solid-state laser system with a new version of a pulse compression scheme based on stimulated Brillouin scattering is proposed. The scheme allows us to work in a wide energy range from 100 mJ to several Joules, with a compressed pulse as short as 150-300 ps. [ABSTRACT FROM AUTHOR]

Based on numerical modeling of metallized diffraction gratings with multilayer insulator coatings, the diffraction efficiency of such gratings is investigated, assuming that the initial profile of the metallized grating is not reproduced in the course of sequential deposition of coating layers. From comparison of experimental and calculated data, it is concluded that the initial grating relief is subject to considerable smoothing. The new nontraditional range of the optimum values of layer thicknesses, which provides a high diffraction efficiency in the operating wavelength range of 1.06 µm, is suggested. The stability of the diffraction efficiency with respect to random errors in the thickness of insulator layers deposited is investigated numerically. [ABSTRACT FROM AUTHOR]