arXiv subjects

A. Muraviev

Publications and source records attributed to A. Muraviev.

8 recordsLinked to original sources

arXiv2025

Bridging Mid-IR and Terahertz Domains in a Single High-Resolution Dual-Comb Spectroscopy Measurement

Dual-comb spectroscopy (DCS) utilizes a pair of broadband mutually coherent laser frequency combs to enable high-resolution, high-accuracy spectroscopic measurements with atomic-clock-level frequency referencing, and rapid, multiplexed acquisition without moving parts. It has traditionally been confined to specific domains: terahertz, infrared, visible, and ultraviolet, each requiring distinct comb sources and detection mechanisms tailored to the nature of the spectroscopic target. Yet, similar techniques may be implemented in the terahertz (THz) and mid-infrared (MIR) regions, such as optical rectification for comb generation and electro-optic sampling for detection, both using crystals with quadratic nonlinearity. However, in the Reststrahlen band near phonon resonances in these crystals, typically between 5 and 10 THz, both linear and nonlinear susceptibilities experience abnormally high dispersion, and light propagation is strongly suppressed. This confines DCS operation to spectral regions either below or above the Reststrahlen band and effectively separating the THz and MIR domains. Here we demonstrate high-resolution DCS performed simultaneously over two broad spectral bands, each spanning an octave or more. The measurements cover both the MIR (350-1150 cm$^{-1}$; 8.7-28.5 $μ$m; 10.5-34.5 THz) and the THz region (80-160 cm$^{-1}$; 62.5-125 $μ$m; 2.4-4.8 THz), effectively bridging these traditionally separate regions within a single acquisition. This enables direct cross-referencing of molecular absorption line strengths across widely separated spectral domains. As a proof of concept, we demonstrate the simultaneous acquisition of ro-vibrational and pure rotational absorption spectra of ammonia (NH$_3$) with a spectral resolution of 7.3 MHz (0.00024 cm$^{-1}$), sufficient to fully resolve Doppler-broadened line shapes across the entire measured spectral range.

physics.optics↗

arXiv2024

Dynamics of radiating particles in current sheets with a transverse magnetic field component

Upcoming multipetawatt laser facilities are capable of inducing effects of quantum electrodynamics (QED) in laser-plasma interaction such as strong radiation reaction and QED cascades, both of which can significantly influence the properties and dynamics of laser plasma. This can result in the formation of extreme plasma structures with unprecedented TG levels of quasistatic magnetic fields, for example current sheets or pinch configurations of nanometer scale or smaller. In such structures radiation losses can play a significant role, so the influence of radiation losses onto the evolution of extreme current sheets deserves a separate and thorough investigation. In the current work we develop an analytical model and extend the quasiadiabatic approach describing individual particle motion onto 3D particle motion in the case when radiation reaction is non-negligible. Given that particle motion is determined by (quasi)invariants of non-dissipative motion, we derive how these (quasi)invariants evolve under the influence of radiation losses, quantify this influence and obtain a (quasi)invariant of dissipative motion. This allows reducing the dimensionality of the system of differential equations describing particle motion to just two instead of six. It is also discussed how the presented method can be used in a wider range of problems.

physics.plasm-ph↗

arXiv2021

Particle dynamics governed by radiation losses in extreme-field current sheets

Particles moving in current sheets under extreme conditions, such as those in the vicinity of pulsars or those predicted on upcoming multipetawatt laser facilities, may be subject to significant radiation losses. We present an analysis of particle motion in fields of a relativistic neutral electron-positron current sheet in the case when radiative effects must be accounted for. In the Landau-Lifshitz radiation reaction force model, when quantum effects are negligible, an analytical solution for particle trajectories is derived. Based on this solution, for the case when quantum effects are significant an averaged quantum solution in the semiclassical approach is obtained. The applicability region of the solutions is determined and analytical trajectories are found to be in good agreement with those of numerical simulations with account for radiative effects. Based on these results we gain new insights into current sheet phenomena expected on upcoming laser facilities.

physics.plasm-ph↗

arXiv2020

Strategies for particle resampling in PIC simulations

In particle-in-cell simulations, excessive or even unfeasible computational demands can be caused by the growth of the number of particles in the course of prolific ionization or cascaded pair production due to the effects of quantum electrodynamics. Here we discuss how one can organize a dynamic rearrangement of the ensemble to reduce the number of macroparticles, while maintaining acceptable sampling of an arbitrary particle distribution. The approaches of merging and thinning as well as their variants are discussed and the aspects of use are considered.

physics.comp-ph↗

arXiv2020

Optimized routines for event generators in QED-PIC codes

In recent years, the prospects of performing fundamental and applied studies at the next-generation high-intensity laser facilities have greatly stimulated the interest in performing large-scale simulations of laser interaction with matter with the account for quantum electrodynamics (QED) processes such as emission of high energy photons and decay of such photons into electron-positron pairs. These processes can be modeled via probabilistic routines that include frequent computation of synchrotron functions and can constitute significant computational demands within accordingly extended Particle-in-Cell (QED-PIC) algorithms. In this regard, the optimization of these routines is of great interest. In this paper, we propose and describe two modifications. First, we derive a more accurate upper-bound estimate for the rate of QED events and use it to arrange local sub-stepping of the global time step in a significantly more efficient way than done previously. Second, we present a new high-performance implementation of synchrotron functions. Our optimizations made it possible to speed up the computations by a factor of up to 13.7 depending on the problem. Our implementation is integrated into the PICADOR and Hi-Chi codes, the latter of which is distributed publicly (https://github.com/hi-chi/pyHiChi).

physics.comp-ph↗

arXiv2016

Ultra-bright GeV photon source via controlled electromagnetic cascades in laser-dipole waves

One aim of upcoming high-intensity laser facilities is to provide new high-flux gamma-ray sources. Electromagnetic cascades may serve for this, but are known to limit both field strengths and particle energies, restricting efficient production of photons to sub-GeV energies. Here we show how to create a directed GeV photon source, enabled by a controlled interplay between the cascade and anomalous radiative trapping. Using advanced 3D QED particle-in-cell (PIC) simulations and analytic estimates, we show that the concept is feasible for planned peak powers of 10 PW level. A higher peak power of 40 PW can provide $10^9$ photons with GeV energies in a well-collimated 3 fs beam, achieving peak brilliance ${9 \times 10^{24}}$ ph s$^{-1}$mrad$^{-2}$mm$^{-2}$/0.1${\%}$BW. Such a source would be a powerful tool for studying fundamental electromagnetic and nuclear processes.

physics.plasm-ph↗

arXiv2016

New Optical Gating Technique for Detection of Electric Field Waveforms with Subpicosecond Resolution

We report on the new optical gating technique used for the direct photoconductive detection of short pulses of terahertz radiation with the resolution up to 250 femtoseconds. The femtosecond optical laser pulse time delayed with respect to the THz pulse generated a large concentration of the electron hole pairs in the AlGaAs/InGaAs High Electron Mobility Transistor (HEMT) drastically increasing the conductivity on the femtosecond scale and effectively shorting the source and drain. This optical gating quenched the response of the plasma waves launched by the THz pulse and allowed us to reproduce the waveform of the THz pulse by varying the time delay between the THz and quenching optical pulses. The results are in excellent agreement with the electro-optic effect measurements and with our hydrodynamic model that predicts the ultra-fast transistor plasmonic response at the time scale much shorter than the electron transit time, in full agreement with the measured data.

cond-mat.mtrl-sci↗

arXiv2015

Extended PIC schemes for physics in ultra-strong laser fields: review and developments

We review common extensions of particle-in-cell (PIC) schemes which account for strong field phenomena in laser-plasma interactions. After describing the physical processes of interest and their numerical implementation, we provide solutions for several associated methodological and algorithmic problems. We propose a modified event generator that precisely models the entire spectrum of incoherent particle emission without any low-energy cutoff, and which imposes close to the weakest possible demands on the numerical time step. Based on this, we also develop an adaptive event generator that subdivides the time step for locally resolving QED events, allowing for efficient simulation of cascades. Further, we present a new and unified technical interface for including the processes of interest in different PIC implementations. Two PIC codes which support this interface, PICADOR and ELMIS, are also briefly reviewed.

physics.plasm-ph↗