Bulletin of the Russian Academy of Sciences: Physics最新文献

The so-called method of moments is used to obtain a system of equations for the parameters of a pulse propagating in an isotropic medium with dispersion in the form of a Duhamel integral. A criterion is found for the parameters of the pulse and the medium separating the modes of propagation of soliton-like pulses.

An analysis is performed of the superluminal propagation of resonant and quasi-resonant soliton-like laser pulses in non-equilibrium media. It is shown that such pulses are unstable. However, the superluminal propagation of these pulse profiles can be observed at the initial stage of an instability’s development, due to the mechanism of reshaping.

A representation of liquid water as a real gas is used to modify the van der Waals equation of state for describing isotherms, isochores, and isobars of liquid water in wide ranges of pressure and temperature. The new thermal equation allows the standard transition to thermodynamics while reproducing internal energy U, free energy F, heat capacity C_V, and entropy S.

Results are presented from studying the effect 2D phenomena have on electron beam bunching in single- and multi-beam broadband klystrons. Results from a comparative analysis of beam bunching using 1D and 2D models are presented as well. The causes of errors in determining the output parameters of broadband klystrons obtained using 1D programs are analyzed.

The process of formation and propagation of pulse pairs in a quadratically nonlinear crystal with two waveguides was investigated with varying parameters related to the position of the waveguides relative to each other, delay, and phase ratio between pulses. A change in the pulse propagation mode during the approach of waveguides and a dependence of the interaction between the pulses on the initial phase ratio were found.

The authors discuss their latest research in the generation and ultrafast control of light-induced dynamic microcavities and photonic time crystals arising from the collision of half-cycle pulses in a medium. The possibility of guiding microcavities during the collision of self-induced transparency half-cycle pulses of the same polarity is demonstrated.

It is shown that for a high-current relativistic Ka-band gyrotron operating in the chaotic generation mode on the lowest mode of a circular waveguide TE_1,1, effective radiation is possible at the seventh harmonic of the gyrofrequency on the TE_7,2 mode. The relative width of the spectrum of chaotic sub terahertz radiation can exceed 5% at a megawatt output power level.

The dynamical effect of an electric field on domain walls in magnetic films with inhomogeneous magnetoelectric interaction is considered. It is shown that both homogeneous and inhomogeneous electric fields induce the excitation of spin waves.

Features are considered of the construction of closed equations for the mean field of acoustic waves with discontinuous profiles in a randomly inhomogeneous medium. Different approaches to obtaining such equations are compared. It is shown that despite the smoothing of profiles on average, a discontinuity in a profile should be considered before averaging. An exact expression is obtained for the mean field of the initial N-wave.

We theoretically considered the possibility to exploit nonlinear Fabry–Pérot interferometers to differential gain of terahertz radiation in the field of a pump wave of the same frequency. It is shown that in a mirrorless nonlinear Fabry–Pérot interferometer, that consists of a crystalline quartz plate and which reflection is determined by Fresnel reflectivity only, the regime of maximal differential gain of radiation with central frequency at 1 THz can be observed at the plate thickness of near 1 mm and radiation intensity of 10⁸ W cm^–2 order.