arXiv subjects

K. A. Ivanov

Publications and source records attributed to K. A. Ivanov.

4 recordsLinked to original sources

arXiv2026

Measurement of the laser pulse phase velocity in plasma channel for DLA optimization

We demonstrate a novel, direct method for measuring the phase velocity $v_ϕ$ of an intense laser pulse within a plasma channel - the crucial parameter that controls the resonance condition in direct laser acceleration (DLA). The technique exploits the second harmonic (SH) radiation generated at the channel sheath - a phenomenon previously observed in laser-wakefield acceleration experiments. The SH emission angle is governed by a phase-matching condition that directly depends on $v_ϕ$. Experimental measurements performed using a 1 TW, 10 Hz Ti:Sa laser system yield phase velocities in the range $v_ϕ=(1.010-1.030)c$ for plasma electron densities in the range $n_e=(0.01-0.06)n_{cr}$. The diagnostic is validated through quasi-3D particle-in-cell (PIC) simulations that reproduce the experimental conditions. This work provides a way to optimize DLA schemes by enabling in-situ measurement of the laser pulse phase velocity in plasma channels.

physics.plasm-ph↗

arXiv2024

Polarization state control for high peak power applications

Numerous applications in the extreme field science are possible with circularly polarized high peak power ultrashort pulses. Commonly used quarter wave plates are not applicable here, while multi-mirror schemes are very complicated. We showed that the simple PET film $\approx$20 $μ$m thick can be used to control the polarization state of the high peak power beam and achieve ellipticity of $\approx$0.8 with negligible nonlinear phase distortion. The film can withstand $10^3$ shots at intensity of $I = 3 \cdot 10^{12}$ W/cm$^2$ without visible damage. Thus, for a PW laser system and beam diameter of 20 cm the PET film can be used for quite a long time. We proved this experimentally using 1 TW femtosecond Ti:Sa laser measuring the angular distribution of the second harmonic from the plasma channel created in an undercritical gas plume.

physics.plasm-ph↗

arXiv2018

Different regimes of Purcell Effect in Disordered Photonic Crystals

We demonstrate that disorder in photonic crystals could lead to pronounced modification of spontaneous emission rate in the frequency region corresponding to the photonic band gap (PBG). Depending on the amount of disorder, two different regimes of the Purcell effect occurs. For the moderate disorder, an enhancement of spontaneous emission occurs at the edge of PBG due to modification of the properties of the edge state. This effect is responsible for recently observed mirrorless lasing in photonic crystals at the edge of PBG. When the level of disorder increases, the spontaneous emission rate enhances within the PBG due to the appearance of the high quality factor states. This effect is likely responsible for a superlinear dependence of emissions on the pumping observed in synthetic opals.

physics.optics↗

arXiv2012

Double bosonic stimulation of THz emission in a polaritonic cascade laser

We have considered a system of equidistant polaritonic states, interacting with an electromagnetic field of a localized THz cavity mode. An accumulation of photons in a THz cavity mode together with bosonic stimulation of the transition between polariton levels induces intensive radiative scattering of polaritons. The concept of double bosonic stimulation of a radiative transition in a bosonic cascade laser (BCL) is formulated, and the possibility of the use of a BCL for the emission of THz radiation is investigated. The system demonstrates threshold-like behaviour and, above threshold, cascade radiative transitions of polaritons which leads to an increase of quantum efficiency, which can exceed unity. The interaction of polaritons with a reservoir leads to an increase in the threshold pumping rate and a decrease of quantum efficiency.

physics.optics↗