arXiv subjects

Anton Husakou

Publications and source records attributed to Anton Husakou.

At least 19 recordsLinked to original sources

arXiv2026

Strong-field electro-optic sampling of light

We report the experimental realization of electro-optic sampling of light utilizing strong-field light-matter interaction. We show that in contrast to the perturbative regime where the non-linear signal (eg. sum-frequency generation) is localized at the narrowband spectrum that must match the local oscillator, the strong-field regime relies on the generation of a supercontinuum that automatically fulfills the overlaps with a local oscillator providing extremely broadband detection bandwidth. We develop a semi-classical model, benchmark it against the experiments with carrier-envelope-phase (CEP) stable sub-3 femtosecond pulses of octave-spanning bandwidth, and further validate it by a first-principle time-dependent density functional (TDDFT) theory. Our work establishes a simple electro-optic approach for investigating broadband high-frequency dynamics of matter on sub-cycle timescales with attosecond precision.

physics.optics↗

arXiv2026

A finite-difference model for intense light interactions with dielectrics in the ultrafast ionization regime

We present a computationally efficient model that describes the interaction of intense, ultrashort infrared laser pulses with transparent materials in the strong ionization regime. The model is augmented with a detailed self-consistent description of the local response due to ionization and collisional plasma dynamics. It incorporates the direct solution of Maxwell's equations without approximations and rigorous boundary conditions for the input pulse, allowing us to study the ultrafast formation of over-critical nanoscaled plasmas in dielectric materials under the influence of intense tightly focused laser pulses. We perform a scan of the parameter space, find unexpected optima regimes for different experientially relevant parameters, and explain these maxima based on spatiotemporal dynamics.

physics.plasm-ph↗

arXiv2025

Extreme Ultraviolet High-Harmonic Interferometry of Excitation-Induced Bandgap Dynamics in Solids

Interferometry is a fundamental technique in physics, enabling precise measurements through the interference of waves. High-harmonic generation (HHG) in solids has emerged as a powerful method for probing ultrafast electronic dynamics within crystalline structures. In this study, we employed extreme ultraviolet (XUV) high-harmonic interferometry with phase-locked XUV pulse pairs to investigate excitation-induced bandgap dynamics in solids. Our experiments on amorphous SiO2 and crystalline MgO, complemented by analytical modeling and semiconductor Bloch equation simulations, reveal a correlation between transient bandgap modifications and variations in the phase of harmonic emission. These findings suggest a potential pathway for sub-cycle, all-optical control of band structure modifications, advancing prospects for petahertz-scale electronic applications and attosecond diagnostics of carrier dynamics.

physics.optics↗

arXiv2025

Pulse compression by photoexcitation-induced dynamics of Bragg mirrors

We propose dynamical Bragg mirrors as a means to compress intense short optical pulses. We show that strong-field photoexcitation of carriers changes the refractive index of the layers and leads to motion of the resonance-defined boundary of the Bragg mirror. In a reflection geometry, this counter-propagating motion leads to significant compression of the incident pulse. We utilize a finite-difference time-domain numerical model to predict up to a 6-fold pulse compression in the few-femtosecond regime. Modification of the refractive index and properties of the compressed pulse as a function of the incident pulse parameters are investigated.

physics.optics↗

arXiv2024

Photocurrent-induced harmonics in nanostructures

Photocurrent-induced harmonics appear in gases and solids due to tunnel ionization of electrons in strong fields and subsequent acceleration. In contrast to three-step harmonic emission, no return to the parent ions is necessary. Here we show that the same mechanism produces harmonics in metallic nanostructures in strong fields. Furthermore, we demonstrate how strong local field gradient, appearing as a consequence of the field enhancement, affects photocurrent-induced harmonics. This influence can shed light at the state of electron as it appears in the continuum, in particular, to its initial velocity.

cond-mat.mes-hall↗

arXiv2024

Self-compression of 5-$μ$m pulses in hollow waveguides

We experimentally and numerically investigate self-compression of pulses around 5 $μ$m wavelength in a noble-gas-filled hollow waveguides. We demonstrate spectral broadening of multi-mJ pulses at 4.9 $μ$m and associated pulse compression from 85 fs to 47 fs in the solitonic pulse compression regime. The self-compression resulted in sub-three-cycle pulses with 17 GW peak power in the 1-kHz pulse train. A numerical model is established and benchmarked against the experimental results. It allows further insights into the pulse compression process, such as scaling of the compression as a function of gas pressure and waveguide radius, and predicts pulse compression in sub-cycle regime for realistic input parameters.

physics.optics↗

arXiv2024

Photoionization-induced reflection for benchmarking of the photoionization models in solid

The choice of the most suitable analytic photoionization model in solids is a challenging task with no default solution. Here we show how the best formalism can be determined based on the waveform of the pulse reflected by a sample due to photoionized almost-free electrons in the conduction band. For a typical case of diamond, we compare three simple models and benchmark them against highly accurate first-principle TDDFT simulation, by analysing the fit between the reflected pulses in time and frequency domain. For the aims of this paper, we have developed a software package, called PIGLET, for the FDTD simulation of photoionization-governed propagation, which is now freely available for the scientific community. Furthermore, we show that due to interband contributions for very short sub-10-fs pulses a semi-classical description based on any analytical photoionization model fail to provide an adequate description.

physics.optics↗

arXiv2023

Ionization-induced Susceptibility by Nearly-free Electrons in Gases Influenced by the Coulomb Potential

In the present paper we study the influence of the Coulomb potential on the real and imaginary parts of the plasma-induced susceptibility in a photoionized gas. We show that the real part of the susceptibility is more than one order of magnitude larger due to the action of a Coulomb potential. Surprisingly, the long-range Coulomb potential of the atomic core leads to an additional contribution to the imaginary part of the susceptibility which has no counterpart in the case of a short-range potential. We demonstrate that the origin of this behavior are electrons in states very close to the continuum (nearly-free electrons), and analyze the dependence of the susceptibility on the intensity and wavelengths.

physics.optics↗

arXiv2023

Metallic nanostructures as electronic billiards for nonlinear terahertz photonics

Optical properties of metallic nanoparticles are most often considered in terms of plasmons, the coupled states of light and quasi-free electrons. Here we predict that confinement of electrons inside the nanostructure leads to another, very different, type of resonance, which determines the optical properties in the frequency range significantly below the plasmonic resonance. We demonstrate that closely placed confinement-induces resonances typically join into a single composite "super-resonance" which produces giant nonlinearity at low frequencies. Our simulations show how such nonlinearities can be used for efficient down-conversion of optical pump to terahertz and mid-infrared frequencies in sub-micrometer devices based on nanoparticle composites. We discuss the interaction of these quantum-confinement-induced resonances with the conventional plasmonic ones, as well as the unusual quantum level statistics, adapting here the paradigms of the electronic billiard theory.

physics.optics↗

arXiv2023

Linking High-Harmonic Generation and Strong-Field Ionization in Bulk Crystals

The generation of high-order harmonics in bulk solids subjected to intense ultrashort laser pulses has opened up new avenues for research in extreme nonlinear optics and light-matter interaction on sub-cycle timescales. Despite significant advancement over the past decade, a complete understanding of the involved phenomena is still lacking. High-harmonic generation in solids is currently understood as arising from nonlinear intraband currents, interband recollision and ionization-related phenomena. As all of these mechanisms involve or rely upon laser-driven excitation we combine measurements of the angular dependence of nonlinear absorption and high-order harmonic generation in bulk crystals to demonstrate the relation between high-harmonic emission and nonlinear, laser-induced ionization in solids. An unambiguous correlation between the emission of harmonics and laser-induced ionization is found experimentally, that is supported by numerical solutions of the semiconductor Bloch equations and calculations of orientation-dependent ionization rates using maximally localized Wannier-functions.

physics.optics↗

arXiv2023

Tunable in situ Near-UV Pulses by Transient Plasmonic Resonance in Nanocomposites

We propose a new concept for generation of ultrashort pulses based on transient plasmonic resonance in nanoparticle composites. Photoionization and free-carriers plasma change the susceptibility of nanoparticles on a few-femtosecond scale. This results in a narrow time window during the pump pulse duration when the system is in plasmonic resonance, accompanied by a short burst of the local field. During this process, frequency-tunable few-fs pulses are generated. We elucidate the details of the above mechanism, and investigate the influences of different contributing processes.

physics.optics↗

arXiv2023

Unified Model for a Nonlinear Pulse Propagation in Composites and Optimization of THz Generation

We describe a unified numerical model which allows fast and accurate simulation of nonlinear light propagation in nanoparticle composites, including various effects such as group velocity dispersion, second- and third-order nonlinearity, quasi-free-carrier formation and plasma contribution, exciton dynamics, scattering and so on. The developed software package SOLPIC is made available for the community. Using this model, we analyze and optimize efficient generation of THz radiation by two-color pulses in ZnO/fused silica composite, predicting an efficiency of 3\%. We compare the role of various nonlinear effects contributing to the frequency conversion, and show that optimum conditions of THz generation differ from those expected intuitively.

physics.optics↗

arXiv2021

Characterization of laser-induced ionization dynamics in solid dielectrics

The formation of an electron-hole plasma during the interaction of intense femtosecond laser pulses with transparent solids lies at the heart of femtosecond laser processing. Advanced micro- and nanomachining applications require improved control over the excitation characteristics. Here, we relate the emission of low-order harmonics to the strong laser-field-induced plasma formation. Together with a measurement of the total plasma density we identify the contribution of two competing ionization mechanisms - strong-field and electron-impact ionization.

physics.optics↗

arXiv2021

Femtosecond field-driven on-chip unidirectional electronic currents in nonadiabatic tunnelling regime

Recently, asymmetric plasmonic nanojunctions [Karnetzky et. al., Nature Comm. 2471, 9 (2018)] have shown promise as on-chip electronic devices to convert femtosecond optical pulses to current bursts, with a bandwidth of multi-terahertz scale, although yet at low temperatures and pressures. Such nanoscale devices are of great interest for novel ultrafast electronics and opto-electronic applications. Here, we operate the device in air and at room temperature, revealing the mechanisms of photoemission from plasmonic nanojunctions, and the fundamental limitations on the speed of optical-to-electronic conversion. Inter-cycle interference of coherent electronic wavepackets results in a complex energy electron distribution and birth of multiphoton effects. This energy structure, as well as reshaping of the wavepackets during their propagation from one tip to the other, determine the ultrafast dynamics of the current. We show that, up to some level of approximation, the electron flight time is well-determined by the mean ponderomotive velocity in the driving field.

cond-mat.mes-hall↗

arXiv2019

Raman-Kerr Comb Generation Based on Parametric Wave Mixing in Strongly Driven Raman Molecular Gas Medium

We report on experimental and theoretical demonstration of an optical comb spectrum based on a combination of cascaded stimulated Raman scattering and four-wave mixing mediated by Raman-induced nonresonant Kerr-type nonlinearity. This combination enabled to transform a conventional quasi-periodic Raman comb into a comb with a single and smaller frequency spacing. This new phenomenon is realized using a hollow-core photonic crystal fiber filled with 40 bars of deuterium, and pumped with a high-power picosecond laser. The resultant comb shows more than 100 spectral lines spanning over 220 THz from 800 nm to 1710 nm, with a total output power of 7.1 W. In contrast to a pure Raman comb, a 120 THz wide portion of the spectrum exhibits denser and equally-spaced spectral lines with a frequency spacing of around 1.75 THz, which is much smaller than the lowest frequency of the three excited deuterium Raman resonances. A numerical solution of the generalized nonlinear Schrödinger equation in the slowly varying envelope approximation provides very good agreement with the experimental data. The additional sidebands are explained by cascaded four-wave mixing between pre-existing spectral lines, mediated by the large Raman induced optical nonlinearity. The results open a new route to the generation of optical frequency combs that combine large bandwidth and high power controllable frequency spacing.

physics.optics↗

arXiv2016

Quasi-phase-matched high harmonic generation in corrugated micrometer-scale waveguides

The high harmonic generation in periodically corrugated submicrometer waveguides is studied numerically. Plasmonic field enhancement in the vicinity of the corrugations allows to use low pump intensities. Simultaneously, periodic placement of the corrugations leads to quasi-phase-matching and corresponding increase of the high harmonic efficiency. The optimization of waveguide geometry is performed, and the resulting spectra are analyzed by the means of (1+1)D numerical model.

physics.optics↗

arXiv2012

All-optical delay of images by backward four-wave mixing in metal-nanoparticle composites

We theoretically study a novel method for all-optical delay of images based on backward four-wave mixing in composites containing metal nanoparticles. In this approach a delayed phase conjugate probe pulse is generated by the interaction of two counter-propagating pump beams and a non-collinear shaped probe pulse in the nanocomposite.The fractional delay and the reflectivity for the phase-conjugate signal pulses are studied as function of the input pump intensity. It is shown that this scheme can be used for delayed imaging combined with the elimination of optical diffraction. The advantages of this method include minituarized design, tunable wavelength range up to the telecommunication range and wide bandwidth.

physics.optics↗

arXiv2012

Slow light in dielectric composite materials of metal nanoparticles

We propose a method for slowing down light pulses by using composites doped with metal nanoparticles. The underlying mechanism is related to the saturable absorption near the plasmon resonance in a pump-probe regime, leading to strong dispersion of the probe refractive index and significantly reduced group velocities. By using the non-collinear scheme, it is possible to realize the total fractional delay of 43 or larger values. This scheme promises simple and compact slow-light on-chip devices with tunable delay and THz bandwidth.

physics.optics↗