Anton Pakhomov

Anton Pakhomov
Saint Petersburg State University | SPBU · Faculty of Physics

PhD

About

70
Publications
2,364
Reads
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562
Citations
Introduction
My current research interests include: ● Numerical methods for nonlinear nanophotonics; ● Propagation of few-cycle pulses in nonlinear resonant media; ● Modeling of ultrafast lasers.
Additional affiliations
April 2019 - April 2021
Friedrich Schiller University Jena
Position
  • Researcher
Description
  • Theoretical studies on modeling of the surface second-harmonic generation in semiconductor nanostructures
April 2017 - March 2019
Zuse-Institut Berlin
Position
  • Researcher
Description
  • Finite-element modeling of the surface second-harmonic generation in semiconductor nanostructures
October 2011 - March 2017
Russian Academy of Sciences
Position
  • Researcher
Description
  • Nonlinear spatio-temporal dynamics of semiconductor lasers
Education
September 2008 - June 2014
Samara National Research University
Field of study
  • Applied Matematics and Physics

Publications

Publications (70)
Article
Full-text available
Up to now, full tunability of waveforms was possible only in electronics, up to radio-frequencies. Here we propose a new concept of producing few-cycle terahertz (THz) pulses with widely tunable waveforms. It is based on control of the phase delay between different parts of the THz wavefront using linear diffractive optical elements. Suitable subcy...
Article
We propose a scheme to generate single-cycle terahertz (THz) pulses via reflection of an optical femtosecond pulse train from a thin layer of nonlinear resonant medium. Our method is based on the coherent control of low-frequency oscillations and free induction decay in the medium. The specific single-cycle shape of generated THz pulses requires a...
Article
Full-text available
We analyse possibilities to quantitatively evaluate the surface second-order optical nonlinearity in noncentrosymmetric materials based on polarization-resolved analysis of far-field radiation patterns of second-harmonic generation. We analytically demonstrate that for plane-wave illumination the contribution to the second-harmonic signal from the...
Article
Full-text available
Here we consider coherent mode-locking (CML) regimes in single-section cavity lasers, taking place for pulse durations less than atomic population and phase relaxation times, which arise due to coherent Rabi oscillations of the atomic inversion. Typically, CML is introduced for lasers with two sections, the gain and absorber ones. Here we show that...
Article
We analytically and numerically investigate surface second-harmonic generation (SHG) from a stack of dielectric layers. We develop a theoretical formalism based on the transfer matrix method for the calculation of the surface-driven second-harmonic radiation from multilayer structures and elaborate it for the case of ultrathin dielectric layers usi...
Article
Progress in reducing the duration of light pulses (down to one cycle of field oscillations or less), achieved in the last decades, has made it possible to experimentally observe and study a number of atomic-scale phenomena that occur at ultrafast times. Their study and observation are unavailable with conventional sources of monochromatic laser rad...
Article
We investigate theoretically the nonresonant excitation of vibrational levels in polar molecules by unipolar radiation pulses of duration much shorter than the characteristic period of the molecule's vibration. We consider several profiles of the potential of the interaction of atoms in a diatomic molecule and derive analytically the probabilities...
Article
Unipolar pulses have a nonzero electric pulse area (integral of the electric field strength with respect of time in a given point of space). Due to unidirectional action on charges they can be an efficient tool for ultrafast control of wave packet dynamics in matter, charges acceleration and so one. In this paper, we briefly revise recent advances...
Article
Based on the previously developed theory of transformation (time integration and differentiation) of ultrashort pulses in thin metal films, we study the possibility of time differentiation and integration of unipolar pulses. Unipolar pulses of unusual shape–rectangular and triangular–are considered, and their mutual transformation upon propagation...
Article
We propose a scheme to generate coherent radiation with a tunable frequency spectrum based on the excitation of an inhomogeneous thin layer of a resonant medium by an ultrashort pulse. The Cherenkov-type radiation emitted in a transient stage, i.e., while the excitation wavefront is still propagating over the medium, is shown to contain additional...
Article
In this letter, excitation of discrete levels in a quantum system is considered, when the duration of the driving pulse is changed from multi-cycle to ultra-short half-cycle regime. It is shown that, as the number of optical cycles decreases, the system passes from the periodic-driven regime to the “kick-driven” action. In both cases the effect dep...
Article
A new parameter of “the atomic scale of an electrical area” has been introduced. It shows the effect of unipolar pulses on a quantum system. This parameter is equal to the ratio of the Planck constant to the characteristic size of the quantum system and the electric charge of the quantum particle. This new parameter is universal and can be used to...
Article
We study theoretically the temporal transformations of few-cycle pulses upon linear interaction with ultrathin metallic films. We show that under certain conditions on the film thickness and the pulse spectrum, one obtains the temporal differentiation of the pulse shape in transmission and the temporal integration in reflection. In contrast to prev...
Article
Our recent theoretical studies of generation of ultrashort pulses based on collective spontaneous emission from a thin resonant medium layer excited by a pair of high-frequency (compared to the transition frequency of the medium) pulses are reviewed. The source of generated radiation is a resonant polarization pulse in the medium (“stopped polariza...
Article
Full-text available
We study theoretically a possibility of creation and ultrafast control (erasing, spatial frequency multiplication) of population density gratings in a multi-level resonant medium having a resonance transition frequency in the THz range. These gratings are produced by subcycle THz pulses coherently interacting with a nonlinear medium, without any ne...
Article
Full-text available
In this paper, we revise our recent advances in study of high-efficient methods of sub cycle THz pulse generation and control of their wave shape. These methods are based on coherent control of low frequency oscillations in nonlinear medium excited by infrared femtosecond pulses. Our results showed the possibility of sub – and few-cycle pulse forma...
Article
The most typical way to optically control population of atomic and molecular systems is to illuminate them with radiation, resonant to the relevant transitions. Here we consider a possibility to control populations with the subcycle and even unipolar pulses, containing less than one oscillation of electric field. Despite the spectrum of such pulses...
Conference Paper
In this talk, we discuss recently developed by us methods of unipolar half-cycle pulse generation having attosecond duration in optical range and femtosecond duration in terahertz frequency ranges. Such pulses contain a half period of electric field oscillation and weak decaying tail of opposite polarity (quasi unipolar pulse) or without tail (unip...
Preprint
We propose a novel scheme to generate single-cycle terahertz (THz) pulses via reflection of an optical femtosecond pulse train from a thin layer of nonlinear resonant medium. Our method is based on a coherent control of low-frequency oscillations and free induction decay in the medium. The specific single-cycle shape of generated THz pulses require...
Article
A review of results of an investigation of the theory of optical wave packets with extreme properties with respect to a controllable pulse shape or to the complexity of the internal structure of radiation beam pulses is presented. Special attention is paid to the manifestations of dissipative effects of the electromagnetic energy inflow and outflow...
Article
Our recent studies of methods for obtaining ultrashort light pulses and analysis of the impact of ultrashort optical pulses on classical and quantum micro-objects with the identification of the determining role of the degree of unipolarity of pulses (maximum for strictly unipolar pulses) in the efficiency of direct laser acceleration of charged par...
Article
The interaction of subcycle pulses with quantum systems is considered when the pulse duration becomes much smaller than the timescales of electron oscillations. We show analytically that the interaction process in this case is governed by the electric pulse area. The efficient nonresonant excitation of quantum systems by subcycle pulses with a high...
Article
We study theoretically a novel possibility for the emission of few-cycle pulses via excitation of nonlinear oscillators arranged in a thin circular string by a spot of light moving along the string. Such excitation can be realized by a beam emitted from a source at some distance, when the beam rotates with high constant angular velocity. Here we an...
Article
We show that, using a pair of short terahertz pulses, it is possible to form light-induced gratings of the population difference, which can be applied to control terahertz radiation. The pulses coherently interact with the medium and do not overlap in it. The examined effect opens up new opportunities in terahertz spectroscopy with the use of such...
Article
The propagation of a unipolar light pulse with a duration of less than one period in a two-level resonant amplifying medium is studied theoretically. In the process of amplification, the unipolar pulse becomes bipolar. The effect of the relaxation time on the shape and duration of the amplified pulse is demonstrated. It is found that the electric p...
Article
By numerically solving the system of Maxwell–Bloch equations, we have examined theoretically collisions of extremely short single-cycle and unipolar subcycle pulses in a nonlinear resonant medium under conditions that the light interacts coherently with the medium. The dynamics of the electric field of structures of light-induced polarization and i...
Article
The possibility of generation of quasi-unipolar extremely short pulses (with a duration of several periods of field oscillations) is theoretically analyzed for the excitation of a circular, nonlinear, and resonant medium with a light spot. The light spot rotates along a circle with a velocity that exceeds the speed of light in vacuum, while particl...
Article
Using the method of the Green’s function for a wave equation, it is shown that, in a one-dimensional geometry, the field emitted by a resonant medium that is composed by a system of coupled or free charges is proportional not to the acceleration of charges, as is usually assumed, but, rather, to their velocity that they acquire as a result of the a...
Article
Full-text available
We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this me...
Article
Collisions of unipolar subcycle pulses in a nonlinear resonant medium that coherently interact with it are studied theoretically. The dynamics of spatial polarization structures and population difference that the pulses induce in the medium are analyzed. A surprising feature is that the medium is capable of “remembering” the result of the interacti...
Article
Full-text available
Creation, erasing and ultrafast control of population density gratings using few-cycle optical pulses coherently interacting with resonant medium is discussed. In contrast to the commonly used schemes, here the pulses do not need to overlap in the medium, interaction between the pulses is mediated by excitation of polarization waves. We investigate...
Article
Recently, the possibility of the creation, erasing and ultrafast control of polarization and population inversion gratings by sequences of few-cycle bipolar pulses interacting with a medium in a resonant and coherent way was predicted. In this case, the overlapping of pulses in the medium is not needed for the creation of gratings. In this paper, w...
Article
We demonstrate the possibility of inducing, erasing and extra rapidly controlling population difference gratings resulting from coherent interaction of unipolar subcycle pulses with a resonant medium. Gratings can be produced without overlap of pulses in the medium, which is an important distinction of the proposed approach from the traditional one...
Article
The possibility of diagnosing the linear and nonlinear electrodynamic susceptibilities of media by examining the time profiles of extremely short terahertz radiation pulses (using pulsed terahertz spectroscopy methods) that are incident on a thin layer of a medium under study, are reflected from the layer, and are transmitted through it is shown th...
Article
We have examined examples of nonlinear-photonics devices that are based on the coherent interaction of light with matter. Such interaction takes place if the duration of a light pulse is shorter than the relaxation times T1 and T2 in a resonant medium and if the strength of the light field is so high that Rabi oscillations arise. Theoretical analys...
Article
Recent progress in generation of optical pulses of durations comparable to one optical cycle has presented great opportunities for studies of the fundamental processes in matter as well as time-resolved spectroscopy of ultrafast processes in nonlinear media. It opened up a new area of research in modern ultrafast nonlinear optics and led to appeara...
Article
Full-text available
Specific properties of the radiation emitted by a spatially modulated resonance medium excited by an ultrashort light pulse propagating through the medium at a variable superluminal velocity are analyzed. In so doing, frequencies different from that of the resonance transition of the medium may appear in the emission spectrum. It is demonstrated th...
Article
We present a significantly different reflection process from an optically thin flat metallic or dielectric layer and propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse. Unipolar pulses in reflection arise due to specifics of effectively one-dimensional pulse pro...
Article
Methods recently proposed for generating unipolar pulses in nonlinear media in terahertz and optical electromagnetic ranges are reviewed. Such pulses have nonzero “electric area” (time integral of the field strength over the entire duration of a pulse) and, correspondingly, a significant component of the field with zero frequency, thus exhibiting q...
Article
We study the optical response of a resonant medium possessing nonlinear coupling to an external field driven by a few-cycle pump pulse sequence. We demonstrate the possibility of directly producing unipolar half-cycle pulses from the medium possessing an arbitrary nonlinearity, by choosing the proper pulse-to-pulse distance of the pump pulses in th...
Article
Full-text available
We theoretically examine the effect of external optical injection on the spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active m...
Conference Paper
The paper studies the spontaneous formation of nonlinear optical patterns in broad area lasers. Spatiotemporal transverse dynamics of the laser is described by the Maxwell-Bloch equations (MBE). The instability of the steady-state solution leads to pattern formation. Two different types of instabilities were observed analytically (Hopf and wave). 2...
Article
Full-text available
We study the optical response of a resonant medium possessing the nonlinear coupling to external field under excitation by few-cycle pump pulses. A theoretical approach is developed, allowing to analyze unipolar half-cycle pulse generation in such a geometry. Our approach is applicable for the arbitrary coupling functions as well as arbitrarily cur...
Article
The present paper is concerned with the analytical and numerical investigation of the transverse spatio-temporal instabilities in two-level broad-area lasers for the specific class-B case. We show that the two-level class-B broad-area laser tends to naturally operate in the filamentary state. This is revealed to be provided with two causes. First o...
Article
We study theoretically the optical response of the resonant medium on the few-cycle pulse-driven excitation for different types of the coupling strength to the field. It is demonstrated that the medium can exhibit a specific excitation response depending on the field coupling nonlinearity. Remarkably, the analysis of this response revealed the poss...
Article
We study theoretically a new possibility of unipolar pulse generation in a Raman-active medium excited by a series of few-cycle optical pulses. We consider the case when the Raman-active particles are uniformly distributed along a circle or helix, and demonstrate the possibility of obtaining rectangular unipolar pulses with an arbitrarily long dura...
Conference Paper
Temperature-induced laser dynamics of wide-aperture vertical cavity surface emitting semiconductor lasers (VCSELs) is under investigation. We describe the dynamics of VCSELs with circular and square apertures using the full system of two-dimensional Maxwell-Bloch equations. The results of numerical simulations in near and far fields are shown in de...
Conference Paper
In the present paper we investigated the spatio-temporal instabilities of stationary lasing in class-B broad-area lasers. The onset conditions of filamentary instability and its spatio-temporal characteristics were obtained analytically on the basis of Maxwell-Bloch equations without phase-amplitude coupling. The lasing stabilization capabilities t...
Article
A distributed model of wide-aperture laser based on Maxwell−Bloch equations in onedimensional approximation is considered. It is shown that an increase in the pumping parameter in the system gives rise to a cascade of bifurcations of periodic and quasi-periodic dynamic modes, as a result of which attractors in the form of three-frequency tori can b...
Article
Full-text available
In this paper we investigated the spatio-temporal instabilities of stationary lasing in broadarea class-B lasers. Conditions for the onset of filamentary instability and its spatio-temporal characteristics were obtained analytically. The lasing stabilization capabilities through varying laser parameters were considered. We have also shown that effe...
Article
Full-text available
In this paper, we investigate a model of wide-aperture vertical-cavity surface-emitting semiconductor VCSESL based on the complete set of two-dimensional Maxwell-Bloch equations on circular and square apertures. The results of numerical simulation in near and far fields are shown in relation to frequency detuning, which can be presented in semicond...
Article
The processes of the formation of optical field structures in the transverse profile of wide-aperture laser radiation are studied within the model described by the system of Maxwell-Bloch equations. The main types of instabilities appearing above the second lasing threshold and corresponding mechanisms controlling the laser dynamics at negative fre...

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