Acousto-optic interaction in nanodimensional laser heterostructures.

Comparative research on fine spectrum analysis techniques (static and dynamic) has been carried out. The advantages of the dynamic method for fine spectrum study of heterolaser radiation as a method of study of the spectrum change under ultrasonic strain have been shown. An approach to fine dynamic spectrum analysis has been developed, and the treatment of experimental data on the spectrum dynamics of the InGaAsP/InP structures in the presence of surface acoustic waves has been carried out.

Percolation on correlated networks.

We reconsider the problem of percolation on an equilibrium random network with degree-degree correlations between nearest-neighboring vertices focusing on critical singularities at a percolation threshold. We obtain criteria for degree-degree correlations to be irrelevant for critical singularities. We present examples of networks in which assortative and disassortative mixing leads to unusual percolation properties and new critical exponents.

Dynamics of ferroelectric nanodomains in BaTiO(3) epitaxial thin films via piezoresponse force microscopy.

Ferroelectric nanodomains were created in BaTiO(3) thin films by applying a voltage to a sharp conducting tip of a scanning force microscope (SFM). The films were epitaxially grown on SrRuO(3)-covered (001)-oriented SrTiO(3) substrates by a high-pressure sputtering. They appeared to be single-crystalline with the (001) crystallographic orientation relative to the substrate.

Emitting a-SiO(x)(Er) films and a-SiO(x)(Er)/a-Si:H microcavities doped with Er by remote magnetron sputtering technique.

We have developed the technique of growing amorphous a-SiO(x)(Er) films and a-SiO(x)(Er)/a-Si:H multilayer structures based on spatially separating the processes of the decomposition of an oxygen-silane gas mixture in an rf glow discharge plasma and remote magnetron sputtering of an Er target. This approach allows us to control independently the film deposition rate, the Er-ion concentration and its depth distribution in the film. Time-resolved photoluminescence measurements have shown that films and planar microcavities with an Er-doped active layer exhibit internal quantum efficiency for Er ion emission of ∼75%.

Direct temperature dependence measurements of dark conductivity and two-beam coupling in LiNbO3:Fe.

Direct measurements of dark conductivity were conducted over a broad temperature range in LiNbO(3):Fe. These measurements were performed on a series of crystals, which were cut from the same boule and subjected to different annealing procedures (oxidized, reduced, and as-grown). Activation energies of 0.

The parity-adapted basis set in the formulation of the photofragment angular momentum polarization problem: the role of the Coriolis interaction.

We present a theoretical framework for calculating the recoil-angle dependence of the photofragment angular momentum polarization taking into account both radial and Coriolis nonadiabatic interactions in the diatomic/linear photodissociating molecules. The parity-adapted representation of the total molecular wave function has been used throughout the paper. The obtained full quantum-mechanical expressions for the photofragment state multipoles have been simplified by using the semiclassical approximation in the high-J limit and then analyzed for the cases of direct photodissociation and slow predissociation in terms of the anisotropy parameters.

Resonant light delay in GaN with ballistic and diffusive propagation.

We report on a strong delay in light propagation through bulk GaN, detected by time-of-flight spectroscopy. The delay increases resonantly as the photon energy approaches the energy of a neutral-donor bound exciton (BX), resulting in a velocity of light as low as 2100 km/s. In the close vicinity of the BX resonance, the transmitted light contains both ballistic and diffusive components.

Ferroelectric-specific stark effect in stoichiometric LiNbO3:Fe at room temperature.

By means of EPR spectroscopy of LiNbO(3):Fe at room temperature (RT) it is shown that the Stark effect in ferroelectric crystals can be different from that observed in other materials. Novel properties appear when an external E field reverses the direction of the spontaneous polarization, the direction of the linear Stark shift stays the same with a reversal of the E field. The corresponding spectral line shifts can occur over a long time scale (hours).

Control of a noise-induced transition in a nonlinear dynamical system.

Feedback control is applied to change conditions of a noise-induced transition in a nonlinear second order dynamic system. The mathematical model used in the analysis is a system of two-component equations describing operation of a semiconductor-gas-discharge image converter. The control algorithm is proposed using the speed-gradient method for a linearized model system.

Efficient evaluation of neuron populations receiving colored-noise current based on a refractory density method.

The expected firing probability of a stochastic neuron is approximated by a function of the expected subthreshold membrane potential, for the case of colored noise. We propose this approximation in order to extend the recently proposed white noise model [A. V.

Diffusive radiation in one-dimensional Langmuir turbulence.

We calculate spectra of radiation produced by a relativistic particle in the presence of one-dimensional Langmuir turbulence which might be generated by a streaming instability in the plasma, in particular, in the shock front or at the shock-shock interactions. The shape of the radiation spectra is shown to depend sensitively on the angle between the particle velocity and electric field direction. The radiation spectrum in the case of exactly transverse particle motion is degenerate and similar to that of spatially uniform Langmuir oscillations.

The strong thermoelectric effect in nanocarbon generated by the ballistic phonon drag of electrons.

The thermoelectric power and thermoelectric figure of merit for carbon nanostructure consisting of graphite-like (sp(2)) and diamond-like (sp(3)) regions have been investigated. The probability of electron collisions with quasi-ballistic phonons in sp(2) regions has been analysed for the first time. We have shown that the probability is not small.

Modification of scattering lengths via magnetic dipole-dipole interactions.

We propose a new mechanism for tuning an atomic s-wave scattering length. The effect is caused by virtual transitions between different Zeeman sublevels via magnetic dipole-dipole interactions. These transitions give rise to an effective potential, which, in contrast to standard magnetic interactions, has an isotropic component and thus affects s-wave collisions.

The field emission in the alternative electric fields.

We obtained a growth of the emitting points and a considerable increase in the emission current in the regime of alternative power supply for initially polished flat metal surfaces. Formed surfaces demonstrate sufficient field emission current stability in vacuum from 10(-4) to 10(-6)Torr and good tolerance and maintainability of field emission characteristics after series of explosive emission pulses. In an alternative power supply regime, using a grid as one of the electrodes enabled us to output the field emission electron current about 2 mA after accelerating grid.

Ultrafast optical pumping of spin and orbital polarizations in the antiferromagnetic Mott insulators R(2)CuO(4).

We demonstrate that optical pumping by circularly polarized light at the charge-transfer transition can induce spin and orbital polarizations in the strongly correlated Mott insulators R(2)CuO(4) (R=Pr, Nd, Sm) providing a means of ultrafast nonlinear manipulation of spin states on time scales of less than 150 fs. We propose a model which includes both orbital- and spin-related processes possessing different spectral and temporal properties. This allows us to model the optical response of antiferromagnetic Mott insulators to circularly polarized light and estimate the spin relaxation time as tau(s) approximately 30-50 fs.

InAsSb/InAsSbP double heterostructure lasers for 3-4 micrometer spectral range.

InAsSb/InAsSbP double heterostructure diode lasers for the spectral range of 3-4 microm grown by liquid phase epitaxy have been investigated. The laser tuning was studied as a function of the stripe width. The temperature and current tuning of such lasers was measured.

High power CW (16W) and pulse (145W) laser diodes based on quantum well heterostructures.

We suggested and experimentally confirmed the effective method of internal optical loss reduction by high order mode suppression in a separate confinement quantum well laser heterostructure with asymmetric ultra thick waveguide. Manufacturing of InGaAs/GaAs/AlGaAs laser heterostructure with a 1.7 microm-thick asymmetric waveguide allowed attaining super low value of internal optical loss alphai=0.

Was Earth ever infected by martian biota? Clues from radioresistant bacteria.

Here we propose that the radioresistance (tolerance to ionizing radiation) observed in several terrestrial bacteria has a martian origin. Multiple inconsistencies with the current view of radioresistance as an accidental side effect of tolerance to desiccation are discussed. Experiments carried out 25 years ago were reproduced to demonstrate that "ordinary" bacteria can develop high radioresistance ability after multiple cycles of exposure to high radiation dosages followed by cycles of recovery of the bacterial population.

Propagation of localized longitudinal strain waves in a plate in the presence of cubic nonlinearity.

Possible propagating longitudinal strain solitary waves in a plate are shown to be seriously altered when physical cubic nonlinearity is taken into account in the modeling. This also affects an amplification of the wave due to the transverse instability of plane-localized waves and due to the plane-wave interaction.

Acoustooptic interaction in science and applications.

Main results of acousto-optic investigations in physical acoustics of solids obtained in Ioffe Physico-Technical Institute during recent yeas are presented. Both monocrystals, and glass alloys of different compositions were used as objects of researches. The studies were fulfilled in wide ranges of optical wavelengths (0.

Acousto-electron interaction in InGaAsP/InP laser heterostructures.

The frequency modulation of the heterolaser radiation under the ultrasonic strain has been found out. The dynamic and static analysis of the spectral parameters change caused by the alternating strain has been fulfilled. A model is proposed for describing the experimental data, and their theoretical analysis is performed.

Photodissociation of HBr. 1. Electronic structure, photodissociation dynamics, and vector correlation coefficients.

Ab initio potential energy curves, transition dipole moments, and spin-orbit coupling matrix elements are computed for HBr. These are then used, within the framework of time-dependent quantum-mechanical wave-packet calculations, to study the photodissociation dynamics of the molecule. Total and partial integral cross sections, the branching fraction for the formation of excited-state bromine atoms Br(2P(1/2)), and the lowest order anisotropy parameters, beta, for both ground and excited-state bromine are calculated as a function of photolysis energy and compared to experimental and theoretical data determined previously.

Charge transfer between a superconductor and a hopping insulator.

We develop a theory of the low-temperature charge transfer between a superconductor and a hopping insulator. We show that the charge transfer is governed by the coherent two-electron-Cooper pair conversion process time-reversal reflection, where electrons tunnel into a superconductor from the localized states in the hopping insulator located near the interface, and calculate the corresponding interface resistance. A specific feature of this problem is the interplay between the time-reversal reflection at the interface and transport through the percolation cluster.

Velocity map imaging study of BrCl photodissociation at 467 nm: determination of all odd-rank (K = 1 and 3) anisotropy parameters for the Cl(2P(3/2)0) photofragments.

Resonance-enhanced multiphoton ionization and velocity map imaging of the Cl(2P(3/2)0) fragments of BrCl photolysis at 467.16 nm have been used to obtain a complete set of orientation parameters (with ranks K = 1 and 3) describing the polarization of the electronic angular momentum. The experiments employ two geometries distinguished only by the circular or linear polarization of the photolysis laser beam.

k-Core organization of complex networks.

We analytically describe the architecture of randomly damaged uncorrelated networks as a set of successively enclosed substructures--k-cores. The k-core is the largest subgraph where vertices have at least k interconnections. We find the structure of k-cores, their sizes, and their birthpoints--the bootstrap percolation thresholds.