Spatial Separation of Scalar Light Beams with Orbital Angular Momentum Using a Phase Metasurface

JETP Letters - The concept and design optimization of a polarization-independent dielectric metasurface for the spatial separation of scalar light beams with different values of the orbital angular...     

Quasi-ballistic electron transport in quantum wires

Electron transport in a three-dimensional quantum wire is analyzed by taking into account electron scattering by a single point impurity. It is shown that the magnetoconductance plotted versus chemical potential μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively. The peaks lie near the conductance steps. The thermopower plotted versus μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively.     

Mechanical properties and energy dissipation in ultrafine-grained AMts and V95 aluminum alloys during dynamic compression

The thermomechanical characteristics of ultrafine-grained AMts and V95 aluminum alloys with an average crystallite size of 200–600 nm are experimentally studied during dynamic compression. The alloys are fabricated by dynamic channel angular pressing. It is found that the deformation history of the alloys and the initial characteristics of their structural state affect the subsequent plastic deformation and the dissipation of applied energy. The studies of the thermodynamics of deformation in combination with structural investigations before and after dynamic compression allowed us to reveal the main structural relaxation mechanisms in the materials during dynamic compression and to determine the dissipation abilities of various defect structures.     

Effects of mirror adjustment in a neodymium-glass laser

A misaligned mirror can give rise to complex modes, increased threshold, and an altered spatial distribution of the emission.     

Coherent focusing of high harmonics: a new way towards the extreme intensities

We demonstrate analytically and numerically that focusing of high harmonics produced by the reflection of a few-femtosecond laser pulse from a concave plasma surface opens a new way to unprecedentally high intensities. The key features allowing the boosting of the focal intensity are the harmonics coherency and the small exponent of the power-law decay of the harmonics spectrum. Using similarity theory and direct particle-in-cell simulations, we find that the intensity at the focus scales as I(CHF) alpha a(3)(0)I(0), where a(0) and I(0) alpha a(2)(0) are the dimensionless relativistic amplitude and the intensity of the incident laser pulse. The scaling suggests that due to the coherent harmonic focusing (CHF), the Schwinger intensity limit can be reached using lasers with I(0) approximately 10(22) W/cm(2). The pulse duration at the focus scales as tau(CHF) alpha 1/a(2)(0) and reaches the subattosecond range.     

Relativistic Doppler effect: universal spectra and zeptosecond pulses

We report on a numerical observation of the train of zeptosecond pulses produced by the reflection of a relativistically intense femtosecond laser pulse from the oscillating boundary of an overdense plasma because of the Doppler effect. These pulses promise to become unique experimental and technological tools since their length is of the order of the Bohr radius and the intensity is extremely high proportional, variant 10(19) W/cm(2). We present the physical mechanism, analytical theory, and direct particle-in-cell simulations. We show that the harmonic spectrum is universal: the intensity of nth harmonic scales as 1/n(p) for n<4gamma(2), where gamma is the largest gamma factor of the electron fluid boundary, and p=3 and p=5/2 for the broadband and quasimonochromatic laser pulses, respectively.     

Quantum derivatives and terahertz gain in a superlattice

Simple formulas describing terahertz absorption and gain in a semiconductor superlattice irradiated by a microwave pump field are derived for the case when the signal frequency is a half harmonic of the pump. A simple qualitative analysis provides a geometric interpretation of the derived formulas, which can be used to determine if gain is feasible.     

Variational principles for nonpotential operators

One presents numerous approaches for the construction of variational principles for equations with operators which, in general, are nonpotential. One considers separately linear and nonlinear ordinary differential equations, partial and integropartial differential equations. One constructs and investigates both extremal and stationary variational principles and one gives applications of these principles in theoretical physics and in analytic mechanics. A series of unsolved problems are indicated. The survey is intended for mathematicians, physicists, working in both theoretical and applied areas, as well as for graduate students of physics and mathematics.Translated from Itogi Nauki i Tekhniki, Seriya Sovremennye Problemy Matematiki, Noveishie Dostizheniya, Vol. 40, pp. 3–176, 1992.     

Bound States in the Continuum in Magnetophotonic Metasurfaces

JETP Letters - We analyze the enhancement mechanisms of magneto-optical effects in all-dielectric metasurfaces caused by the bound state in the continuum resonance. In a structure under study, a...