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Dive into the research topics where Dmitry Yu. Zagursky is active.

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Featured researches published by Dmitry Yu. Zagursky.


Proceedings of SPIE | 2017

Detection and identification of substances using noisy THz signal

Vyacheslav A. Trofimov; Irina G. Zakharova; Dmitry Yu. Zagursky; Svetlana A. Varentsova

We discuss an effective method for the detection and identification of substances using a high noisy THz signal. In order to model such a noisy signal, we add to the THz signal transmitted through a pure substance, a noisy THz signal obtained in real conditions at a long distance (more than 3.5 m) from the receiver in air. The insufficiency of the standard THz-TDS method is demonstrated. The method discussed in the paper is based on time-dependent integral correlation criteria calculated using spectral dynamics of medium response. A new type of the integral correlation criterion, which is less dependent on spectral characteristics of the noisy signal under investigation, is used for the substance identification. To demonstrate the possibilities of the integral correlation criteria in real experiment, they are applied for the identification of explosive HMX in the reflection mode. To explain the physical mechanism for the false absorption frequencies appearance in the signal we make a computer simulation using 1D Maxwells equations and density matrix formalism. We propose also new method for the substance identification by using the THz pulse frequency up-conversion and discuss an application of the cascade mechanism of molecules high energy levels excitation for the substance identification.


Optics and Photonics for Counterterrorism, Crime Fighting, and Defence XI; and Optical Materials and Biomaterials in Security and Defence Systems Technology XII | 2015

Principal limitation of standard THz time-domain spectroscopy method of the detection and identification of substance and way of its overcoming

Vyacheslav A. Trofimov; Svetlana A. Varentsova; Irina G. Zakharova; Dmitry Yu. Zagursky

We demonstrate principal limitations of standard Time Domain Spectroscopy based on a broadband THz pulse for the detection and identification of substance using paper napkins as a sample. To avoid these limitations we propose a new high effective algorithm for this purpose. We demonstrate its applicability in realistic and simulated situation for various substances under consideration. The interaction of a THz pulse with a disordered layered structure was simulated in order to show the influence of the disordered layers on the spectral characteristics of the transmitted and reflected signals. Spectral characteristics of these signals were analyzed in a direct comparison with the spectrum of the incident pulse as well as by means of Spectral Dynamics Analysis method and integral correlation criteria. The efficiency of the detection and identification method, based on integral correlation and likeness criteria, is confirmed on the basis of computer simulation. To demonstrate the possibilities of the integral correlation criteria in real experiment, they were applied for the identification of explosive HMX in the reflection mode.


PLOS ONE | 2018

Conservative finite-difference scheme for the problem of THz pulse interaction with multilevel layer covered by disordered structure based on the density matrix formalism and 1D Maxwell’s equation

Vyacheslav A. Trofimov; Svetlana A. Varentsova; Irina G. Zakharova; Dmitry Yu. Zagursky

On the basis of the Crank-Nicolson method, we develop a conservative finite-difference scheme for investigation of the THz pulse interaction with a multilevel medium, covered by a disordered layered structure, in the framework of the Maxwell-Bloch equations, describing the substance evolution and the electromagnetic field evolution. For this set of the partial differential equations, the conservation laws are derived and proved. We generalize the Bloch invariant with respect to the multilevel medium. The approximation order of the developed finite-difference scheme is investigated and its conservatism property is also proved. To solve the difference equations, which are nonlinear with respect to the electric field strength, we propose an iteration method and its convergence is proved. To increase the computer simulation efficiency, we use the well-known solution of Maxwell’s equations in 1D case as artificial boundary condition. It is approximated using Cabaret scheme with the second order of an accuracy. On the basis of developed finite-difference scheme, we investigate the broadband THz pulse interaction with a medium covered by a disordered structure. This problem is of interest for the substance detection and identification. We show that the disordered structure dramatically induces an appearance of the substance false absorption frequencies. We demonstrate also that the spectrum for the transmitted and reflected pulses becomes broader due to the cascade mechanism of the high energy levels excitation of molecules. It leads to the substance emission at the frequencies, which are far from the frequency range for the incident pulse spectrum. Time-dependent spectral intensities at these frequencies are weakly disturbed by the disordered cover and, hence, they can be used for the substance identification.


Proceedings of SPIE | 2016

THz TDS of substance covered by disordered structure

V. A. Trofimov; Dmitry Yu. Zagursky; Irina G. Zakharova

Computer simulation of a few-cycle pulse interaction with a substance covered by disordered structure is performed in order to study the effects imposed on spectra of transmitted and reflected pulses by presence of the cover. The substance is described by semi-classic approach and the cover is described by classic electrodynamics equations for linear isotropic medium. The cover consists of a number of layers with different properties which is considered to be the cause of the distortions. The influence of relation between pulse wavelength and cover layer thickness is illustrated. Computer simulation results are compared with those of physical experiments conducted for paper and other common materials.


Terahertz Emitters, Receivers, and Applications VIII | 2017

Substance identification by pulsed THz spectroscopy in the presence of disordered structure

Vyacheslav A. Trofimov; Irina G. Zakharova; Dmitry Yu. Zagursky; Svetlana A. Varentsova

We discuss an effective method for the detection and identification of a substance, covered by a disordered structure, using the pulsed THz signal. The insufficiency of the standard THz-TDS method, based on the comparison of substance absorption spectra from database with the absorption spectrum of the substance under investigation, is demonstrated. To explain a physical mechanism of false absorption lines appearance in the signal we make a computer simulation on the base of 1D Maxwells equations and density matrix formalism. For the detection and identification of substance we propose to utilize substance emission at high frequencies corresponding to the high energy levels excitation under the THz pulse action due to the cascade mechanism. In the case of a non-resonant medium we also discuss second harmonic generation and a possibility of its application to the substance detection and identification. The proposed method of the substance detection and identification is based on time-dependent integral correlation criteria calculated with the help of the spectral dynamics of medium response. A new type of the integral correlation criterion, which is less dependent on spectral characteristics of the noisy signal under investigation, is used for the identification.


Sensors | 2017

New Possibilities of Substance Identification Based on THz Time Domain Spectroscopy Using a Cascade Mechanism of High Energy Level Excitation

Vyacheslav A. Trofimov; Svetlana A. Varentsova; Irina G. Zakharova; Dmitry Yu. Zagursky

Using an experiment with thin paper layers and computer simulation, we demonstrate the principal limitations of standard Time Domain Spectroscopy (TDS) based on using a broadband THz pulse for the detection and identification of a substance placed inside a disordered structure. We demonstrate the spectrum broadening of both transmitted and reflected pulses due to the cascade mechanism of the high energy level excitation considering, for example, a three-energy level medium. The pulse spectrum in the range of high frequencies remains undisturbed in the presence of a disordered structure. To avoid false absorption frequencies detection, we apply the spectral dynamics analysis method (SDA-method) together with certain integral correlation criteria (ICC).


Counterterrorism, Crime Fighting, Forensics, and Surveillance Technologies | 2017

New approach for detection and identification of substances using THz TDS

Irina G. Zakharova; Vyacheslav A. Trofimov; Dmitry Yu. Zagursky; Svetlana A. Varentsova

We propose and discuss new effective approach for the detection and identification of substances using a THz TDS. It consists in using a substance emission at high frequencies corresponding to high energy levels relaxation due to cascade mechanism of their excitation under the broadband THz pulse action. The second approach is based on a possibility of observing the absorption frequencies of substance under the frequency up-conversion. To explain a physical mechanism of considered possibilities we make a computer simulation using 1D Maxwells equations and density matrix formalism.


international conference on multimedia information networking and security | 2016

Pulsed THz TDS of objects covered by disordered structure

V. A. Trofimov; Irina G. Zakharova; Dmitry Yu. Zagursky; Svetlana A. Varentsova

Using both computer simulation and physical experiment, we demonstrate principal limitations of standard Time Domain Spectroscopy based on a broadband THz pulse for the detection and identification of substance placed inside the disordered structure. The interaction of a THz pulse with a disordered layered structure was simulated in order to show the influence of the disordered layers on the spectral characteristics of the transmitted and reflected signals. Spectral characteristics of these signals were analyzed in a direct comparison with the incident pulse spectrum. We showed that a disordered structure disturbs the reflected pulse spectrum dramatically. To avoid this, we used the integral correlation criteria in real experiment. Computer simulation results were confirmed by physical experiment. We provided the experiments with paper bag, and ordinary sheets of paper, and napkins.


days on diffraction | 2016

Broadening of few-cycle THz pulse spectrum at electromagnetic energy absorption in multi-level medium

Vyacheslav A. Trofimov; Dmitry Yu. Zagursky; Irina G. Zakharova

Influence of the polarization relaxation times on the cascade mechanism of high energy level excitation is investigated. Appearance of this mechanism in any situation is shown.


Proceedings of SPIE | 2016

Influence of disordered cover on cascade mechanism of medium response spectrum broadening at THz-TDS of substance

Vyacheslav A. Trofimov; Dmitry Yu. Zagursky; Irina G. Zakharova

Remote sensing using the pulsed THz-TDS is of great interest because of its possible practical applications. Many ordinary materials (paper, for example) are transparent to THz radiation while the hazardous substances, which have to detect, possess fingerprints in this frequency range. However, covers of ordinary material can distort its spectrum in such a way that the spectrum of reflected THz pulse or transmitted THz pulse will contain absorption frequencies, which are inherent to dangerous substance (explosives, illistic drugs....), despite their absence in the material under consideration. On the other hand, it is well-known that the spectrum of medium response under the action of THz pulse is broader than the incident THz pulse spectrum. This is a result of a possibility of high energy level excitation due to cascade mechanism of their excitation. For practical point of view, it is very important to know about features of a covering substance influence on the medium response spectrum broadening. This problem is investigated in our report using the computer simulation. We carry out computer simulation of a few-cycle electromagnetic pulse interaction with a substance exhibiting nonlinear non-instantaneous response. An influence of the pulse duration and polarization relaxation rate on the pulse interaction with an uncovered medium and with a medium, which is covered by a linear disordered structure, is investigated. We demonstrate that the spectra of reflected or transmitted pulses may comprise multiple additional spectral lines, caused by various transitions between energy levels of molecules. The spectral intensity of these energy level transitions is affected by the pulse duration and the effective time of interaction which depends on polarization relaxation rate as well as the medium layer thickness.

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