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  • Victor Georgievich Bespalov
Victor Georgievich Bespalov

Victor Georgievich Bespalov
ITMO University | SPbNRU ITMO · Department of Photonics and Optical Information Technology

Doctor Phys.-Math. Science, Proffessor

About

212
Publications
9,607
Reads
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1,242
Citations
Additional affiliations
January 1996 - present
ITMO University
Position
  • Professor
September 1978 - January 2005
Vavilov State Optical Institute
Position
  • Head of Department

Publications

Publications (212)
Article
This paper presents a brief review of the developed laser technologies and lidars with hyperspectral resolution and extremely high sensitivity for the diagnosis of complex impurities in the atmosphere and hydrosphere via Raman spectra. The technological foundations of the research, exploratory, and ecological studies of hydrocarbons are developed u...
Article
Full-text available
A modification of the Z-scan technique for measuring nonlinear refractive index n2 in the terahertz spectral region is proposed. Measurements are made at a broadband terahertz radiation intensity of 0.8 × 10⁹ W cm⁻². Coefficient n2 = 2.5 × 10⁻¹¹ cm² W⁻¹ is estimated for semiconductor crystalline ZnSe.
Article
Full-text available
In this paper we present results of experimental study of two-photon absorption (2PA) induced in electro-optical crystals ZnTe and ZnSe by intensive optical radiation in 450? 950 nm wavelength range. These crystals are of interest due to common usage in THz systems. Femtosecond pump-probe spectroscopy with the supercontinuum source helps to induce...
Article
Full-text available
We present the results of our experimental investigation of the transmission of plates of zinc-selenide crystal doped with iron at a level of 0.23 mass % in the terahertz-frequency range and compare them with the transmission of undoped samples. We show that the presence of iron impurities in a zinc-selenide sample makes the medium more transparent...
Article
This paper describes a laser system that provides dual-pulse bispectral excitation of a laser plasma in an extreme- UV source for nanolithography in this spectral region. The radiation converter is based on a low-power YAG:Nd laser and a powerful CO2 laser. A saturating signal is injected into the power stage of a CO2 amplifier by subnanosecond pul...
Article
Full-text available
In this paper, we demonstrate experimentally for the first time (to our knowledge) the generation of spectral supercontinuum (SC) of more than two octaves with high intensity in a water jet. The spectrum of the generated SC extends from 350 to 1400 nm, with intensities up to 10¹¹ W/cm², and its generation efficiency is more than 50%. For the pump i...
Conference Paper
The ultrafast wireless information transmission method using sliced spectral continuum in the THz frequency range, formed by a pair of THz pulses, is presented. The sliced spectral continuum contained 31 spectral lines with 23 GHz spacing in the range from 0.04 to 0.75 THz transmitted via 2 meters of free-space by common THz time-domain spectromete...
Article
Full-text available
The unique properties of narrowband and broadband terahertz Bessel beams have led to a number of their applications in different fields, for example, for the depth of focusing and resolution enhancement in terahertz imaging. However, broadband terahertz Bessel beams can probably be also used for the diffraction minimization in the short-range broad...
Article
Full-text available
Orbital angular momentum (OAM) represents new informational degree of freedom for data encoding and multiplexing in fiber and free-space communications. OAM-carrying beams (also called vortex beams) were successfully used to increase the capacity of optical, millimetre-wave and radio frequency communication systems. However, the investigation of th...
Article
Full-text available
We present the study on spatial distribution of the maximum of terahertz field amplitude in time domain when generated by a femtosecond filament. It is shown that as a result of the propagation of the terahertz field forms a spherical wave front, on the edge of which the maximum of amplitude has a temporary delay in contrary to its central part.
Article
Full-text available
A mathematical model of linear and nonlinear processes is presented occurring under the influence of femtosecond laser radiation on the skin. There was held an analysis and the numerical solution of an equation system describing the dynamics of the electron and phonon subsystems were received. The results can be used to determine the maximum permis...
Article
Full-text available
We present a mathematical model of linear and nonlinear processes that takes place under the action of femtosecond laser radiation on the cutaneous covering. The study is carried out and the analytical solution of the set of equations describing the dynamics of the electron and atomic subsystems and investigated the processes of linear and nonlinea...
Article
Theoretical analysis of the spatial, noise, and energy characteristics of an amplifier has been performed in the mode of spectral and time selection using subnanosecond stimulated Raman Scattering gain of weak echo signals in crystalline active media that are known for high (up to 10–1 cm/MW) gain coefficients. The possibility to reach high gain va...
Conference Paper
The paper presents a mathematical model of linear and nonlinear processes occurring due to propagation of femtosecond laser pulses in vitreous of the human eye. By methods of numerical simulation, we have solved a nonlinear spectral equation describing dynamics of two-dimensional TE-polarized radiation. The solution was performed in a homogeneous i...
Article
Full-text available
Terahertz pulse time-domain holography (THz PTDH) is the powerful technique for high-resolution amplitude and phase THz imaging that allows mapping spectroscopic information across the imaged object. In this paper, we consider most sought after applications of phase imaging provided by this technique and experimentally demonstrate the ability of th...
Conference Paper
The lenses with coaxial mirrors allow obtain NA values up to of 0.8 and demagnification β ≥10. The larger β value leads to the mask cost reducing, as in this case, the elements of the IC pattern template can be made bigger and, therefore, with fewer defects. Сoaxial schemes can engender a problem of the image plane shift beyond the projection lens...
Conference Paper
The power consumption in the two-pulse bispectral primary source could be substantially decreased by replacing the SRS converters from 1.06 μm into 10.6 μm wavelength as the preamplifier cascades in СО2 laser channel at the same efficiency radiation of EUV source. The creation of high volume manufacturing lithography facilities with the technologic...
Conference Paper
New concept of EUV radiation power scaling in the intermediate focus of the illumination system is proposed. The multiplex source scheme based on combination of several sources with acceptable level power allows to concentrate EUV light on the total power level of 1kW and more have been developed. The experimental results showed that the power cons...
Article
Principles of recording the amplitudes and phases of wave fields in the terahertz (THz) frequency range are considered and methodology and schemes used for imaging in this range are analyzed. Generation of THz radiation by femtosecond optical pulses and registration of THz electric field waveforms allow the methods for holographic recording and ima...
Conference Paper
Frequency comb in terahertz spectrum with element bandwidth of 0.03 THz utilizing high-power pulsed source are obtained. Data encoding and transmission via terahertz frequency comb are demonstrated. Information encoded in frequency comb by Si plate filter transferred on 60 cm in spectrum of two terahertz pulses.
Article
There are already significant amounts of hazardous radioactive substances in the world. It, potentially, leads to a major damage and contamination of large areas. Laser sensing can serve as a highly effective method of searching and monitoring of radioactive contamination. We developed a laser system to detect accidental leakage of radioactive mate...
Article
Over the past 100 years, the rate of temperature in the Arctic increases almost twice higher than the average rate of warming of the planet. Identifying methane anomalies responsible for the temperature increase, by hiking trails in the Arctic requires great human labor. It is necessary to use lidar methods for search and identification of methane...
Article
We have demonstrated airborne lidar possessing spectral resolution λ/Δλ ≥ 1000. Its ultraspectral resolution is provided by the dual polychromator based on large-sized stigmatic holographic gratings. The lidar was tested in a real-life flight conditions at the transcontinental gas pipeline. It has performed aero search of leaks and measurements of...
Conference Paper
The results of experimental and theoretical modeling of multistage Raman conversion in compressed hydrogen with a buffer gas under using the lasing of neodymium-crystalline mediums to obtain the seed radiation for CO2 power amplifier in the double-pulse and bispectral primary laser while maintaining efficiency of LPP EUV source are presented. This...
Conference Paper
Full-text available
In this paper we consider using the terahertz (THz) time domain spectroscopy (TDS) for non destructive testing and determining the chemical composition of the vanes and rotor-blade spars. A versatile terahertz spectrometer for reflection and transmission has been used for experiments. We consider the features of measured terahertz signal in tempora...
Article
It is shown that the power consumption in the double-pulse bi-spectral primary source for EUV lithography can be substantially decrease by replacing pre-amplifiers in power CO2 laser with the SRS converters wavelength 1.06 μm to 10.6 μm while maintaining efficiency of EUV radiation output of illuminated plasma.
Article
Full-text available
The experimental setup of versatile pulse terahertz reflection and transmission spectrometer and operation concept were described. Using this setup the temporary forms of THz signal reflected from and transmitted through the samples like amino acids, dental tissue and normal were obtained. The possibility of structural determination of powdered med...
Article
Full-text available
The increasing majority of mobile devices, hotspots, the emergence of video formats with ultra-resolution and growing amount of stored and transmitted data led to the demand of higher throughput and data rate wireless communications. Thus, several approaches have been developed to achieve high data rates in wireless networks. It is shown that the m...
Article
Full-text available
Two detection systems, electro-optical system and photoconducting system, are tested by the method suggested previously for determining the boundaries of broadband terahertz radiation in time-domain spectroscopy. From a series of measurements the error in determining the operation ranges is calculated. The terahertz spectrometer with an electro-opt...
Conference Paper
We have developed airborn lidar system to detect pipeline leakage and explore oil and gas deposits. Test flights indicate that a sensitivity of 6 ppm for methane and 3 ppm for hydrogen sulfide has been reached for leakage detection. As estimations have shown the reliability of HHG detection can exceed 80% at the integration method of seismic prospe...
Article
Remote laser spectroscopy availability for airborne search of radionuclides polution has been examined. Experiments were carried out under the CARS circuit. The method of remote detection a radionuclide in atmosphere from container burial places and in places of recycling the fuel waste of the atomic power station is elaborated. Preliminary results...
Article
Full-text available
This investigation presents a method of determining the frequency band of pulsed terahertz spectrometer for reliable research and technique for scan time decrease. Both methods lead to consistency and acceleration of data.
Article
Full-text available
Paper presents tunable terahertz broadband phase-only modulator based on CdSe - CdS. It produces linear phase shift in broadband THz wave controlled by modulator illumination and bias voltage.
Article
We developed a Raman lidar with ultraspectral resolution for automatic airborne monitoring of pipeline leaks and for oil and gas exploration. Experiments were carried out under the CARS circuit. Minimal concentrations of 200 ppb of heavy hydrocarbon gas have been remotely measured in laboratory tests. Test flights indicate that a sensitivity of 6 p...
Article
Full-text available
A numerical reconstruction of spatial distributions of optical radiation propagating through a volume of nonlinear medium at input and output planes of the medium was demonstrated using a scheme of digital holography. A nonlinear Schrodinger equation with Fourier Split-Step method was used as a tool to propagate wavefront in the volume of the mediu...
Article
Full-text available
We numerically investigated the influence of wavelength of terahertz radiation and size of scanning pinhole on the quality of reconstructed image by terahertz pulse time domain holography method. The improvement of the quality is achieved mainly by reducing the wavelength of the radiation, pinhole size and pinhole step (value of the pinhole displac...
Article
Full-text available
Coherent properties of supercontinuum sources are highly significant for various applications, including low-coherence interferometry and optical frequency metrology. We propose a fast method for the spatial and temporal self-coherence of the SC measurement using Michelson interferometer without a mirror movement. Furthermore, we present self-coher...
Article
Spectroscopic and tomographic studies on the solid tissues of a human tooth have been carried out in the terahertz (THz) frequency range. It is experimentally shown that, in samples of dental tissue damaged by caries, the absorption lines of water in the THz region have higher intensity by comparison with the intensity of healthy tissue. The radiat...
Conference Paper
We developed a Raman lidar with ultraspectral resolution for automatic airborne monitoring of pipeline leaks and for oil and gas exploration. Test flights indicate that a sensitivity of 6 ppm for methane and 2 ppm for hydrogen sulfide has been reached for leakage detection. The lidar is based on the CARS method with a Ti:Sapphire pump laser and a f...
Conference Paper
The structural scheme of underwater laser spectroscopic system for hydrocarbon deposits exploration was considered. This equipment can be used to scan from the ship in aqueous environments with limited visibility, and spectral-temporal analysis of the Raman scattering of the hydrocarbons in these environments.
Conference Paper
The migration of oil and gas and other molecules such as H2S, CO, CO2, H2, He leads to a change in the physical properties of the rocks above the deposit and the formation of halos of methane, propane, and other hydrocarbons in the surface sediments and the atmospheric boundary layer with anomalous concentrations of hydrocarbon gases. We have devel...
Conference Paper
Laser sensing can serve as a highly effective method of searching and monitoring of radioactive contamination. The first method is essence consists in definition the Sr90 and Сs137 concentration by excitation and registration of fluorescence at wavelength of λ = 0.347÷7.0 μm at laser sounding. The second method experiments were carried out under th...
Conference Paper
We developed a Raman lidar with ultraspectral resolution for automatic airborne monitoring of pipeline leaks and for oil and gas exploration. Test flights indicate that a sensitivity of 6 ppm for methane and 2 ppm for hydrogen sulfide has been reached for leakage detection.
Chapter
Full-text available
It is known that intensity-dependent phase changes (by temporal self-action effects) and intensity changes (by spatial self-action effects) distort the wavefront of light as it propagates through the medium [1], therefore one can not propagate images directly through a nonlinear medium [2] (indirect methods can be used, but they do not allow to mea...
Conference Paper
Full-text available
We present latest results obtained in the scope of imaging methods which allows one to recover spatial phase distribution in the terahertz wave-fields. One of these methods is the terahertz pulse time-domain holography. The second one is the iterative phase retrieval approach, transferred from the visible frequency range. Index Terms—Terahertz digi...
Article
Full-text available
In order to determine the limits of the biologically safe maximum allowable levels of pulsed terahertz (THz) radiation, a prototype of apparatus has been developed for the irradiation of cell cultures immersed in a liquid medium with broad-band THz radiation in the 0.05-1.2 THz frequency range. The action of THz radiation on the functional activity...
Article
Full-text available
In this paper, we present review and latest results obtained in the scope of terahertz holographic and other methods for phase retrieval in terahertz imaging. Not only accurate change of amplitude, but also rigorous phase retrieval is essential for precise calculation of optical parameters of the samples in terahertz range. Pulse terahertz holograp...
Conference Paper
Results of supercontinuum generation experiments in case of excitation by optical pulses with central wavelength 828 nm, duration 40-50 fs, energy up to 1,0-1,5 mJ are presented. Supercontinuum radiation was detected in crystal DKDP and other crystals with χ(2)-nonlinearity at range from 400 nm to 1450 nm, as well as up to 2300 nm, where radiation...
Article
Full-text available
In this paper, the results of using the method of angular spectrum of plane waves as a mathematical model of the iterative algorithm for phase retrieval based on the intensity distributions formed by the radiation of THz frequency range are presented. This mathematical model is designed to calculate the wave field propagation in the near-field diff...
Article
Full-text available
Application of terahertz radiation for the creation of medical equipment and solving of biological problems has become widely spread. From this point of view, the influence of THz radiation on the nerve fibers is of primary concern. In addition, several studies indicated both stimulating and depressive effects on nerve cells. However, the mechanism...
Article
Full-text available
Using the infrared matrix of pyroelectric or other photodetectors along with THz band pass filters with pulsed or CW sources one can record the 2D intensity distribution of THz radiation with a high degree of monochromatization. This allows one to use various approaches to solving the phase problem which were developed for the visible frequencies....
Article
Full-text available
Additional datasets allow the wavefront phase retrieval by the iteration procedure. They can be obtained in practice using the set of parameters in the phase analyzer, radiation and registration systems of the phase retrieval setups.
Article
Analytical expressions are obtained for the spatial distribution of the temporal spectra of paraxial waves consisting of one complete vibration of the electromagnetic field in the regions of Fresnel and Fraunhofer diffraction and for the spatiotemporal distribution of their field in the region of Fraunhofer diffraction. It is shown that, when such...
Article
Full-text available
An iterative wavefront retrieval method based on intensity measurements formed by several wavelengths is investigated in the present contribution. This multiwavelength technique is extended to use the intensity distributions recorded in various planes of the volume speckle field. The ability to retrieve the wavefront using speckle patterns is demon...
Article
The results of a theoretical analysis of the generation of broadband radiation in the infrared and terahertz spectral ranges upon the excitation of plasma in air by two femtosecond pulses at the fundamental and second-harmonic frequencies of a Ti-sapphire laser are presented. It is found that the appearance of long-wavelength radiation in a strong...
Article
Full-text available
This paper presents the results of studies of how broad-band terahertz radiation of the range 0.1-2THz affects individual biological systems. Samples of biological tissue have different extinction coefficients, which differ in healthy and pathological tissues. The transmittance of tissue samples for pulsed terahertz radiation depends on their thick...
Article
This article is devoted to a study of the optical properties of the new material polyparaxylylene-Ag, which is of interest as a promising material for creating optics elements.