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V.P. Kandidov

Other affiliations: Russian Academy of Sciences
Bio: V.P. Kandidov is an academic researcher from Moscow State University. The author has contributed to research in topics: Femtosecond & Filamentation. The author has an hindex of 32, co-authored 166 publications receiving 3800 citations. Previous affiliations of V.P. Kandidov include Russian Academy of Sciences.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors investigated the long light filaments generated in air by powerful ultrashort laser pulses, previously attributed to self-channeling, using a Ti:sapphire chirped-pulse-amplification laser system.
Abstract: The long light filaments generated in air by powerful ultrashort laser pulses, previously attributed to self-channeling, were investigated by use of gigawatt pulses from a Ti:sapphire chirped-pulse-amplification laser system. A filament contained only a small fraction of the pulse energy and always ended at the diffraction length of the beam (~100 m), independently of the pulse energy. These features are explained by the moving-focus model, which is presented as an alternative to the self-channeling model. Computer simulations involving ionization of the air also support the moving-focus model.

336 citations

Journal ArticleDOI
TL;DR: The state of the art of investigations on filamentation of a high-power femtosecond laser radiation in transparent media is reviewed in this article, where the physical picture of this phenomenon is presented and its relation to the fundamental concepts of nonlinear optics and practical applications is demonstrated.
Abstract: The state of the art of investigations on filamentation of a high-power femtosecond laser radiation in transparent media is reviewed. The physical picture of this phenomenon is presented and its relation to the fundamental concepts of nonlinear optics and practical applications is demonstrated. Experimental and theoretical methods are briefly considered and laser radiation parameters in the case of filamentation are given. The review can be of interest both for specialists and researches wanting to become familiar with a new, rapidly developing direction in laser physics.

258 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of light field on the whole transverse scale of the beam, including its edges.
Abstract: We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp.

246 citations

Journal ArticleDOI
TL;DR: It was found that the conical emission accompanying the filamentation of powerful ultrashort laser pulses in air originates from self-phase modulation in the plasma produced by the pulse during propagation.
Abstract: We performed detailed experimental and numerical investigations of the conical emission (CE) accompanying the filamentation of powerful ultrashort laser pulses in air. It was found that the CE originates from self-phase modulation in the plasma produced by the pulse during propagation. The experiment and the simulation agree on the essential features of the CE: The CE angle decreases with increasing wavelength and is independent of the position along the filament, and there is no CE at Stokes-shifted wavelengths.

229 citations

Journal ArticleDOI
TL;DR: In this paper, the competition between femtosecond laser pulse induced optical breakdown and filamentation in condensed matter is studied both experimentally and numerically using water as an example, and the coexistence of filamentation and breakdown is observed under tight focusing conditions.
Abstract: The competition between femtosecond laser pulse induced optical breakdown and femtosecond laser pulse filamentation in condensed matter is studied both experimentally and numerically using water as an example. The coexistence of filamentation and breakdown is observed under tight focusing conditions. The development of the filamentation process from the creation of a single filament to the formation of many filaments at higher pulse energy is characterized systematically. In addition, strong deflection and modulation of the supercontinuum is observed. They manifest themselves at the beginning of the filamentation process, near the highly disordered plasma created by optical breakdown at the geometrical focus.

178 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the main aspects of ultrashort laser pulse filamentation in various transparent media such as air (gases), transparent solids and liquids are introduced and discussed.

2,282 citations

Journal ArticleDOI
TL;DR: In this article, the working mechanisms of femtosecond laser nanoprocessing in biomaterials with oscillator pulses of 80-MHz repetition rate and with amplified pulses of 1-kHz repetition rate were investigated.
Abstract: We review recent advances in laser cell surgery, and investigate the working mechanisms of femtosecond laser nanoprocessing in biomaterials with oscillator pulses of 80-MHz repetition rate and with amplified pulses of 1-kHz repetition rate. Plasma formation in water, the evolution of the temperature distribution, thermoelastic stress generation, and stress-induced bubble formation are numerically simulated for NA=1.3, and the outcome is compared to experimental results. Mechanisms and the spatial resolution of femtosecond laser surgery are then compared to the features of continuous-wave (cw) microbeams. We find that free electrons are produced in a fairly large irradiance range below the optical breakdown threshold, with a deterministic relationship between free-electron density and irradiance. This provides a large ‘tuning range’ for the creation of spatially extremely confined chemical, thermal, and mechanical effects via free-electron generation. Dissection at 80-MHz repetition rate is performed in the low-density plasma regime at pulse energies well below the optical breakdown threshold and only slightly higher than used for nonlinear imaging. It is mediated by free-electron-induced chemical decomposition (bond breaking) in conjunction with multiphoton-induced chemistry, and hardly related to heating or thermoelastic stresses. When the energy is raised, accumulative heating occurs and long-lasting bubbles are produced by tissue dissociation into volatile fragments, which is usually unwanted. By contrast, dissection at 1-kHz repetition rate is performed using more than 10-fold larger pulse energies and relies on thermoelastically induced formation of minute transient cavities with lifetimes <100 ns. Both modes of femtosecond laser nanoprocessing can achieve a 2–3 fold better precision than cell surgery using cw irradiation, and enable manipulation at arbitrary locations.

1,226 citations

Journal ArticleDOI
TL;DR: Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials, thereby enabling the fabrication of bioconjugates and heterogeneous catalysts.
Abstract: Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

892 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the landmarks of the 10-odd-year progress in this field, focusing on the theoretical modeling of the propagation equations, whose physical ingredients are discussed from numerical simulations.
Abstract: Modern laser sources nowadays deliver ultrashort light pulses reaching few cycles in duration and peak powers exceeding several terawatt (TW). When such pulses propagate through optically transparent media, they first self-focus in space and grow in intensity, until they generate a tenuous plasma by photo-ionization. For free electron densities and beam intensities below their breakdown limits, these pulses evolve as self-guided objects, resulting from successive equilibria between the Kerr focusing process, the chromatic dispersion of the medium and the defocusing action of the electron plasma. Discovered one decade ago, this self-channeling mechanism reveals a new physics, widely extending the frontiers of nonlinear optics. Implications include long-distance propagation of TW beams in the atmosphere, supercontinuum emission, pulse shortening as well as high-order harmonic generation. This review presents the landmarks of the 10-odd-year progress in this field. Particular emphasis is laid on the theoretical modeling of the propagation equations, whose physical ingredients are discussed from numerical simulations. The dynamics of single filaments created over laboratory scales in various materials such as noble gases, liquids and dielectrics reveal new perspectives in pulse shortening techniques. Far-field spectra provide promising diagnostics. Attention is also paid to the multifilamentation instability of broad beams, breaking up the energy distribution into small-scale cells along the optical path. The robustness of the resulting filaments in adverse weathers, their large conical emission exploited for multipollutant remote sensing, nonlinear spectroscopy and the possibility of guiding electric discharges in air are finally addressed on the basis of experimental results.

858 citations

Journal ArticleDOI
04 Jul 2003-Science
TL;DR: The mobile femtosecond-terawatt laser system, Teramobile, has been constructed to study the applications of white-light and nonlinear light detection and ranging applications for atmospheric trace-gas remote sensing or remote identification of aerosols.
Abstract: Most long-path remote spectroscopic studies of the atmosphere rely on ambient light or narrow-band lasers. High-power femtosecond laser pulses have been found to propagate in the atmosphere as dynamically self-guided filaments that emit in a continuum from the ultraviolet to the infrared. This white light exhibits a directional behavior with enhanced backward scattering and was detected from an altitude of more than 20 kilometers. This light source opens the way to white-light and nonlinear light detection and ranging applications for atmospheric trace-gas remote sensing or remote identification of aerosols. Air ionization inside the filaments also opens promising perspectives for laser-induced condensation and lightning control. The mobile femtosecond-terawatt laser system, Teramobile, has been constructed to study these applications.

800 citations