arXiv subjects

Vladislav S. Yakovlev

Publications and source records attributed to Vladislav S. Yakovlev.

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↗

arXiv2025

A general approximator for strong-field ionization rates

We address the long-standing problem of determining accurate, time-resolved ionization rates for atoms in strong laser fields, a quantity that is fundamental to attosecond science. We show that it is possible to retrieve sub-optical-cycle dynamics of strong-field ionization from ionization probabilities obtained for a set of few-cycle laser pulses that covers a sufficiently broad parameter space. To this end, we introduce the General Approximator for Strong-Field Ionization Rates (GASFIR), a retrieval tool that uses a few adjustable parameters to accurately reconstruct ab initio data. By imposing only essential physical constraints, our model provides a versatile framework for time-domain investigations of strong-field ionization and the role of ionization dynamics in attosecond metrology and lightwave electronics.

physics.atom-ph↗

arXiv2025

Plasmascopy of ultrafast hot charges in solids

We demonstrate an electric field-resolved approach for probing ultrafast dynamics of photoinjected charges in solids. Direct access to the electric field of few-cycle pulses enables us to measure a broadband response of a medium with associated plasma frequency. We prepare an ensemble of photoinjected hot charge carriers with energies sufficient to trigger impact ionization and establish a framework to measure its dynamics. Our study reveals the first time-resolved observation of the short-lived ultrafast impact ionization in germanium counteracted by trapping of mobile charges at later times. This approach provides a promising route for studying ultrafast many-body physics in photoexcited solids, with predictions from advanced theoretical models.

cond-mat.other↗

arXiv2021

Ultra-broadband photonic sampling of optical waveforms

Direct access to the electric field of light provides a subcycle view of the polarization response of matter, thus enabling sensitive metrology in physics, chemistry, and medicine. Optical-field sampling techniques take advantage of some process that lasts much less than an optical cycle of the measured light wave. Most of them rely on the generation of free electrons either by a weak extreme ultraviolet pulse or by a strong optical pulse. The ability of such techniques to detect weak signals is limited by undesirable effects associated with ionization. An alternative is all-optical methods, where the fast process is a nonlinear wave mixing. Such photonic methods may rely on extreme ultraviolet or optical pulses. They typically have better sensitivity, but smaller bandwidth. Here we propose generalized heterodyne optical-sampling techniques (GHOSTs), which overcome the bandwidth limit through controlling light-pulse waveforms.

physics.optics↗

arXiv2021

The emergence of macroscopic currents in photoconductive sampling of optical fields

Photoconductive field sampling is a key methodology for advancing our understanding of light-matter interaction and ultrafast optoelectronic applications. For visible light the bandwidth of photoconductive sampling of fields and field-induced dynamics can be extended to the petahertz domain. Despite the growing importance of ultrafast photoconductive measurements, a rigorous model for connecting the microscopic electron dynamics to the macroscopic external signal is lacking. This has caused conflicting interpretations about the origin of macroscopic currents. Here, we present systematic experimental studies on the macroscopic signal formation of ultrafast currents in gases. We developed a theoretical model based on the Ramo-Shockley-theorem that overcomes the previously introduced artificial separation into dipole and current contributions. Extensive numerical particle-in-cell (PIC)-type simulations based on this model permit a quantitative comparison with experimental results and help to identify the roles of electron scattering and Coulomb interactions. The results imply that most of the heuristic models utilized so far will need to be amended. Our approach can aid in the design of more sensitive and more efficient photoconductive devices. We demonstrate for the case of gases that over an order of magnitude increase in signal is achievable, paving the way towards petahertz field measurements with the highest sensitivity.

physics.optics↗

arXiv2020

Transient optical gain in strong-field-excited solids

Multiphoton excitation of a solid by a few-cycle, intense laser pulse forms a very non-equilibrium distribution of charge carriers, where occupation probabilities do not necessarily decrease with energy. We show that, under certain conditions, significant population inversion can emerge between pairs of valence- or conduction-band states, where transitions between the Bloch states are dipole-allowed. This population inversion leads to stimulated emission in a laser-excited solid at frequencies where the unperturbed solid is transparent. We establish the optimal conditions for observing the strong-field-induced optical gain.

cond-mat.mes-hall↗

arXiv2018

Ensemble properties of charge carriers injected by an ultrashort laser pulse

The average effective mass of charge carriers produced by an intense ultrashort laser pulse in a transparent solid increases significantly as the excitation mechanism changes from multiphoton transitions to interband tunneling. We theoretically investigate this phenomenon for several dielectrics and semiconductors. For diamond as a representative dielectric, we present a detailed analysis of the laser-induced change of optical properties. When the concentration of free carriers is high, we find that the average effective mass controls not only the intraband charge-carrier transport but also the interband contributions to the optical response. We observe that the excitation-induced birefringence is particularly large for parameters where the plasma response compensates for the linear response of an unperturbed solid.

cond-mat.mes-hall↗

arXiv2018

Strong-field Phenomena in Periodic Systems

The advent of visible-infrared laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of ultrafast processes in semiconductors and dielectrics (bulk as well as nanostructured), motivated by the quest for the ultimate frontiers of electron-based signal metrology and processing. Exploring ways to approach those frontiers requires insight into the physics underlying the interaction of strong high-frequency (optical) fields with electrons moving in periodic potentials. This Colloquium aims at providing this insight. Introduction to the foundations of strong-field phenomena defines and compares regimes of field--matter interaction in periodic systems, including (perfect) crystals as well as optical and semiconductor superlattices, followed by a review of recent experimental advances in the study of strong-field dynamics in crystals and nanostructures. Avenues toward measuring and controlling electronic processes up to petahertz frequencies are discussed.

quant-ph↗

arXiv2018

Near-field Surface Waves in Few-Layer MoS2

Recently emerged layered transition metal dichalcogenides have attracted great interest due to their intriguing fundamental physical properties and potential applications in optoelectronics. Using scattering-type scanning near-field optical microscope (s-SNOM) and theoretical modeling, we study propagating surface waves in the visible spectral range that are excited at sharp edges of layered transition metal dichalcogenides (TMDC) such as molybdenum disulfide and tungsten diselenide. These surface waves form fringes in s-SNOM measurements. By measuring how the fringes change when the sample is rotated with respect to the incident beam, we obtain evidence that exfoliated MoS2 on a silicon substrate supports two types of Zenneck surface waves that are predicted to exist in materials with large real and imaginary parts of the permittivity. We have compared MoS2 interference fringes with those formed on layered insulator such as hexagonal boron nitride where only leaky modes are possible due to its small permittivity. Interpretation of experimental data is supported by theoretical models. Our results could pave the way to the investigation of surface waves on TMDCs and other van der Waals materials and their novel photonics applications.

cond-mat.mes-hall↗

arXiv2017

Ultrafast optical Faraday effect in transparent solids

We predict a strong-field ultrafast optical Faraday effect, where a circularly polarized ultrashort optical pulse induces transient chirality in an achiral transparent dielectric. This effect is attractive for time-resolved measurements because it gives access to the non-instantaneity of the nonlinear medium response, and also because it represents relaxation of time-reversal symmetry by all-optical means. We propose probing the induced transient chirality with a weak linearly polarized ultraviolet pulse that is shorter than the near-infrared pump pulse. The predicted effects are ultrafast: the induced chirality vanishes for probe delays exceeding the duration of the near-infrared pulse. This opens up possibilities for applications in ultrafast circular-polarization modulators and analyzers.

cond-mat.other↗

arXiv2017

Adiabatic corrections for velocity-gauge simulations of electron dynamics in periodic potentials

We show how to significantly reduce the number of energy bands required to model the interaction of light with crystalline solids in the velocity gauge. We achieve this by deriving analytical corrections to the electric current density. These corrections depend only on band energies, the matrix elements of the momentum operator, and the macroscopic vector potential. Thus, the corrections can be evaluated independently from modeling the interaction with light. In addition to improving the convergence of velocity-gauge calculations, our analytical approach overcomes the long-standing problem of divergences in expressions for linear and nonlinear susceptibilities.

physics.comp-ph↗

arXiv2016

Sub-cycle optical control of current in a semiconductor: from the multiphoton to the tunneling regime

Nonlinear interactions between ultrashort optical waveforms and solids can be used to induce and steer electric current on a femtosecond (fs) timescale, holding promise for electronic signal processing at PHz frequencies [Nature 493, 70 (2013)]. So far, this approach has been limited to insulators, requiring extremely strong peak electric fields and intensities. Here, we show all-optical generation and control of directly measurable electric current in a semiconductor relevant for high-speed and high-power (opto)electronics, gallium nitride (GaN), within an optical cycle and on a timescale shorter than 2 fs, at intensities at least an order of magnitude lower than those required for dielectrics. Our approach opens the door to PHz electronics and metrology, applicable to low-power (non-amplified) laser pulses, and may lead to future applications in semiconductor and photonic integrated circuit technologies.

cond-mat.mes-hall↗

arXiv2015

Strong-Field Resonant Dynamics in Semiconductors

We predict that a direct bandgap semiconductor (GaAs) resonantly excited by a strong ultrashort laser pulse exhibits a novel regime: kicked anharmonic Rabi oscillations (KARO). In this regime, Rabi oscillations are strongly coupled to intraband motion, and interband transitions mainly take place during short times when electrons pass near the Brillouin zone center where electron populations undergo very rapid changes. Asymmetry of the residual population distribution induces an electric current controlled by the carrier-envelope phase. The predicted effects are experimentally observable using photoemission and terahertz spectroscopies.

cond-mat.mes-hall↗

arXiv2015

Ultrafast control of strong-field electron dynamics in solids

We review theoretical foundations and some recent progress related to the quest of controlling the motion of charge carriers with intense laser pulses and optical waveforms. The tools and techniques of attosecond science enable detailed investigations of a relatively unexplored regime of nondestructive strong-field effects. Such extremely nonlinear effects may be utilized to steer electron motion with precisely controlled optical fields and switch electric currents at a rate that is far beyond the capabilities of conventional electronics.

cond-mat.mes-hall↗

arXiv2014

The Effect of Multiple Conduction Bands on High Harmonic Emission from Dielectrics

We find that, for sufficiently strong mid-IR fields, transitions between different conduction bands play an important role in the generation of high-order harmonics in a dielectric. The transitions make a significant contribution to the harmonic signal, and they can create a single effective band for the motion of an electron wave packet. We show how high harmonic spectra produced during the interaction of ultrashort laser pulses with periodic solids provide a spectroscopic tool for understanding the effective band structure that controls electron dynamics in these media.

cond-mat.other↗

arXiv2013

The effect of dynamical Bloch oscillations on optical-field-induced current in a wide gap dielectric

We consider the motion of charge carriers in a bulk wide-gap dielectric interacting with a few-cycle laser pulse. A semiclassical model based on Bloch equations is applied to describe the emerging time-dependent macroscopic currents for laser intensities approaching the damage threshold. At such laser intensities, electrons can reach edges of the first Brillouin zone even for electron-phonon scattering rates as high as those known for SiO_2. We find that, whenever this happens, Brag-like reflections of electron waves, also known as Bloch oscillations, affect the dependence of the charge displaced by the laser pulse on its carrier-envelope phase.

cond-mat.mes-hall↗

arXiv2013

Theory of strong-field injection and control of photocurrent in dielectrics and wide bandgap semiconductors

We propose a theory of optically-induced currents in dielectrics and wide-gap semiconductors exposed to a non-resonant ultrashort laser pulse with a stabilized carrier-envelope phase. In order to describe strong-field electron dynamics, equations for density matrix have been solved self-consistently with equations for the macroscopic electric field inside the medium, which we model by a one-dimensional potential. We provide a detailed analysis of physically important quantities (band populations, macroscopic polarization, and transferred charge), which reveals that carrier-envelope phase control of the electric current can be interpreted as a result of quantum-mechanical interference of multiphoton excitation channels. Our numerical results are in good agreement with experimental data.

cond-mat.mtrl-sci↗

arXiv2013

Quantum beats in the polarization response of a dielectric to intense few-cycle laser pulses

We have investigated the polarization response of a dielectric to intense few-cycle laser pulses with a focus on interband tunnelling. Once charge carriers are created in an initially empty conduction band, they make a significant contribution to the polarization response. In particular, the coherent superposition of conduction- and valence-band states results in quantum beats. This quantum-beat part of the polarization response is affected by the excitation dynamics and attosecond-scale motion of charge carriers in an intense laser field. Our analysis shows that, with the onset of Bloch oscillations or tunnelling, the nonlinear polarization response becomes sensitive to the carrier-envelope phase of the laser pulse.

physics.atom-ph↗