Polarization dynamics of intracavity frequency-doubled Nd:YAG laser

Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser.     

Symmetric random walks in random environments

We consider a random walk on thed-dimensional lattice ^d where the transition probabilitiesp(x,y) are symmetric,p(x,y)=p(y,x), different from zero only ify–x belongs to a finite symmetric set including the origin and are random. We prove the convergence of the finite-dimensional probability distributions of normalized random paths to the finite-dimensional probability distributions of a Wiener process and find our an explicit expression for the diffusion matrix.     

Switching Channel Development Dynamics in Planar Structures on the Basis of Vanadium Dioxide

The results of the experimental studies and numerical simulation of the switching channel development dynamics in planar structures on the basis of vanadium dioxide are reported. The obtained data on the variation of the temperature in the channel with time and of the current arisen after the pulsed load, and on the times of transition from the high-resistance to the low-resistance state and back are analyzed in order to determine the switching mechanism and to predict the functional characteristics of the switchable vanadium- oxide structures as promising materials for the creation of relaxation generators that can serve as prototypes of neural oscillators. It is shown that the switching behavior is associated with the metal–semiconductor phase transition in vanadium dioxide, which is stimulated by the emission of Joule heat.     

The Use of Galvanic Displacement for Synthesizing Pt/Carbide (Mo2C,ZrC, NbC) Catalysts Highly Active in the Hydrogen Evolution Reaction

Russian Journal of Electrochemistry - The composite materials involving platinum nanoparticles on the surface of carbides of Mo, Zr, and Nb are synthesized by the currentless redox reaction between...     

Chemical Composition of Glass and Traditions of Enamellers in Eastern Europe in the Late Roman Period (a Case Study of the Bryansk Hoard)

Crystallography Reports - The chemical composition of Bryansk hoard enamels (late II?III century) has been investigated by scanning electron microscopy and electron probe microanalysis. Raw...     

On Effective Conductivity on ℤ d Lattice

We study the effective conductivity _e for a random wire problem on the d-dimensional cubic lattice ^d , d2 in the case when random conductivities on bonds are independent identically distributed random variables. We give exact expressions for the expansion of the effective conductivity in terms of the moments of the disorder parameter up to the 5th order. In the 2D case using the duality symmetry we also derive the 6th order expansion. We compare our results with the Bruggeman approximation and show that in the 2D case it coincides with the exact solution up to the terms of 4th order but deviates from it for the higher order terms.     

Bose condensation of excitons in two-layer electronic systems in the absence of magnetic field

A high narrow peak of interlayer differential tunnel conductivity is observed at low temperatures in heterostructures with two closely located electronic layers in the absence of magnetic field. The analysis of experimental results suggests that this peak is due to the interlayer phase coherence that arises in the system as a result of the Bose condensation of interlayer excitons (electron-hole pairs) belonging to different layers, in accordance with the recent theoretical predictions.     

Mixing for some classes of special flows over rotations of the circle

Landau Institute of Theoretical Physics, RAN. Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 26, No. 3, pp. 1–21, July–September, 1992.     

Multimode fabry-perot laser: Number of relaxation frequencies

We study analytically the Tang, Statz, and deMars equations describing a solid-state Fabry-Perot laser to determine how many relaxation oscillations it displays. When the modes have equal gains, the number of relaxation oscillations varies between zero and the mode number, depending on the laser parameters. In particular, a large number of modes or a relatively large pumping rate leads to the elimination of all relaxation oscillations except one, thereby simplifying the noise spectrum. These results are generalized to include unequal modal gains such as might result from the Lorentzian gain profile. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia; Universite Libre de Bruxelles, Bruxelles, Belgium. Published from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, Nos. 1–2, pp. 161–175, January–February, 1997.