Exceptional surface wave as a condition of the maximum increase in the intensity of an evanescent electromagnetic wave in a transparent medium

It has been shown that the condition of the maximum increase in the intensity of TM or TE evanescent electromagnetic waves at the interface between two transparent insulators in a static electric (magnetic) field simultaneously determines the dispersion law of the corresponding exceptional surface wave for which the instantaneous energy flux through the interface is zero at any time.     

On chaotic dynamics in "pseudobilliard" Hamiltonian systems with two degrees of freedom

A new class of Hamiltonian dynamical systems with two degrees of freedom is studied, for which the Hamiltonian function is a linear form with respect to moduli of both momenta. For different potentials such systems can be either completely integrable or behave just as normal nonintegrable Hamiltonian systems with two degrees of freedom: one observes many of the phenomena characteristic of the latter ones, such as a breakdown of invariant tori as soon as the integrability is violated; a formation of stochastic layers around destroyed separatrices; bifurcations of periodic orbits, etc. At the same time, the equations of motion are simply integrated on subsequent adjacent time intervals, as in billiard systems; i.e., all the trajectories can be calculated explicitly: Given an initial data, the state of the system is uniquely determined for any moment. This feature of systems in interest makes them very attractive models for a study of nonlinear phenomena in finite-dimensional Hamiltonian systems. A simple representative model of this class (a model with quadratic potential), whose dynamics is typical, is studied in detail. (c) 1997 American Institute of Physics.     

Generalized Approximation of Strong Interaction of Waves in the Theory of High-Power Radiation Frequency Doubling

The approximation of strong interaction of waves is developed to analyze the generation of the second harmonic under the conditions of self-action. Based on this method, an approximate expression is obtained for the generation efficiency of the second harmonic with allowance for the effect of higher nonlinearities, depletion of pumping radiation, and linear phase detuning. The effect of phase detuning and change in the spatial distribution of the amplitude of the fundamental radiation on the efficiency of second-harmonic generation has been analyzed. Good agreement of the results of the developed approximate method with experimental data and numerical calculations is shown. The optimum conditions of the second-harmonic generation in a wide range of the laser system radiation intensities are determined.     

Interaction of kinks for semilinear wave equations with a small parameter

We consider a class of semilinear wave equations with a small parameter and nonlinearities such that the equations have exact kink-type solutions. The main result consists in obtaining sufficient conditions for the nonlinearities under which the interaction of kinks preserves the sine-Gordon scenario. This means that the interaction occurs without changing the waves shape and with shifts of trajectories.     

Classification of cocycles of generic equivalence relations

We study cocycles of an ergodic generic countable equivalence relation ℜ modulo meager sets. Two cocycles of ℜ are called weakly equivalent if they are cohomologous up to an element of Aut ℜ. It is proved that two nontransient cocycles with values in an arbitrary countable group are weakly equivalent if and only if their generic Mackey actions are isomorphic.     

Ionization self-compression of intense femtosecond pulses propagating through gas-filled dielectric capillaries

A mechanism of the ionization-induced self-compression of femtosecond laser pulses propagating in a gas-filled hollow dielectric capillary has been investigated both experimentally and theoretically. In particular, the double self-compression of a laser pulse from 76 to 40 fs has been experimentally demonstrated. A theoretical model that explains the mechanism of such a self-compression and provides a good agreement with the experimental data has been developed. The model also predicts that a laser pulse shorter than 10 fs can be generated in the optimal regime with an energy efficiency exceeding the efficiency of self-compression on a filament widely discussed at present.     

Ten-Megawatt Pulsed Gyrotron with a 1-cm Wavelength and a 50% Efficiency

Development of a gyrotron driven by a relativistic electron beam and generating radiation at the wavelength 1 cm with an output power of 10 MW, an efficiency of 50%, and a pulse duration of a few hundreds of nanoseconds is reported.     

Generation of squeezed states on reflection of light from a system of free electrons

The statistical characteristics of an electromagnetic wave reflected from a system of successive free-electron mirrors are investigated. Such a configuration of the electron stream is characteristic in particular for free-electron lasers. An expresson is obtained for the squeeze factor of the field of the reflected wave, and the optimal geometric configuration of the system of electrons is found. Numerical estimates show that the squeezing can be substantial when the number of electronic mirrors is large. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 160–165 (10 February 1996)     

Remote monitoring of surfaces of optical elements

Potentialities for remote measurement of parameters of working surfaces of optical elements and remote detection of the appearance of defects of such surfaces are studied experimentally. The method suggested in this paper is based on the use of a nonlinear optical image intensifier consisting of a phase-conjugating mirror and laser preamplifiers. A sensitivity of about two signal photons per pixel limited by the quantum noise level is achieved in remote measurements of the angular distribution of diffuse reflection from optical surfaces.     

Properties of evanescent waves in polarized media in a constant external electric field: II. The noncompensated antiferromagnetic

The effect of gyrotropy on the character of formation and propagation of evanescent waves of the TM and TE types in the presence of a constant external electric field is studied by an example of the two-sublattice model of a centrally symmetric antiferromagnetic in the easy-plane, weak ferromagnetic phase.