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

A theoretical and numerical investigation was made of the optical implementation of the second-order spatial differentiation operation using a layered metal–dielectric structure at normal light beam incidence. Numerical simulation results confirmed the theoretical results and showed the possibility of optical calculation of the Laplace operator at normal incidence with high quality.

The spectral method was used to solve the problem of interaction of short optical pulses with PT‑symmetric photonic crystals under conditions of frequency singularity. It was shown that, at a small deviation from the exceptional point of spontaneous decay of PT-symmetric field modes, frequency singularities of the transmission and reflection coefficients of the structure arise. This leads to a significant narrowing of the pulse spectra and an increase in their amplitude and duration with unidirectional Bragg reflection.

The diffraction transformation of wave fractal fields is considered. It is shown that, when light beams with a speckle structure propagate in optical systems and in free space, their fractal properties have a high degree of stability.

A potential wave motion along a free surface of a deep ideal fluid has been studied. The exact solutions of the equations of motion with the physically validated boundary conditions on a free surface have been obtained. The shape of the free surface has been studied as a function of the amplitude and the surface characteristics have been highlighted. The characteristics of waves as a function of the nonlinearity parameter have been studied.

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.

2D-PIC numerical simulations were performed to study the generation of X-rays by the interaction of an oncoming laser wave with a relativistic electron mirror formed by a powerful accelerating laser pulse from a plasma layer. The structure of the radiated field in the far zone was investigated, and the spectral density of the radiation field and the angular distribution of the pulse energy were found. Changing the parameters of the accelerating and counterpropagating waves allows one to control the characteristics of the radiation.

Calculations are made for a relativistic gyrotron in the range of 300 GHz with power of up to 8 MW. Large-particle 3D modeling is used to calculate the shape of the output power pulse for the experimentally measured shape of accelerating voltage pulse. It is shown that the full energy of radiation at the operating frequency can exceed 4 J.

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.

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.