Papers by Leonid Skvortsov
Исследовано влияние лазерного излучения на процесс образования налетов на поверхности оптических ... more Исследовано влияние лазерного излучения на процесс образования налетов на поверхности оптических деталей, расположенных в замкнутых объемах, содержащих герметизирующие компаунды типа ВГО-1, КЛТ-30, У-2-28, К-68. Для определения состава налетов применялись методы рентгеновской фотоэлектронной спектроскопии и ИК-спектроскопии; состава газовой среды-метод масс-спектрометрии. Исследованы кинетика образования налетов в зависимости от температуры среды и параметров лазерного излучения. Рассмотрены возможные механизмы образования налетов и методы их устранения.
The effect of laser radiation on the formation of film like deposits on the surface of optical pa... more The effect of laser radiation on the formation of film like deposits on the surface of optical parts located in closed volumes containing sealing compounds such as VGO-1, KLT-30, U-2-28, K-68 has been studied. Methods of X-ray photoelectron spectroscopy and IR spectroscopy were used to determine the composition of the film like deposits; the composition of the gas medium was determined by the method of mass spectrometry. The kinetics of film like deposits formation is investigated depending on the temperature of the medium and the parameters of laser radiation. The possible mechanisms of the formation of film like deposits and methods of their elimination are considered.
Subject of the study. The interaction of mid-infrared (IR) light with a metasurface based on sili... more Subject of the study. The interaction of mid-infrared (IR) light with a metasurface based on silicon scattering elements on a sapphire substrate and its subsequent propagation in the far field were studied. Aim of study. The aim was the development of the metasurface design, its manufacture, and the formation of a vortex beam with a helicoidal wavefront in the medium-wave IR range, measuring the intensity profile of the converted radiation. Method. The finite difference time domain algorithm was used to calculate the characteristics of radiation scattering on the metasurface element. An algorithm of dynamic mode decomposition was applied to analyze the spatial spectrum of radiation obtained as a result of the passage of a plane wave through a plate with the selected design. For the manufacture of the metasurface, the following methods were used: plasma chemical vapor deposition, electron beam lithography, thermal evaporation, atomic layer deposition, reactive ion etching in inductively coupled plasma, and anisotropic cryogenic etching. Main results. A metasurface design was developed for the formation of a laser beam with a helicoidal wavefront in the medium-wave IR range. The parameters of the silicon scattering elements on a sapphire substrate were determined using numerical modeling. The efficiency and characteristics of the spatial spectrum of the constructed metasurface were investigated. It was established that the energy fraction of the secondary harmonics decreased with the distance along the beam propagation. As a result of this work, a vortex beam with an annular intensity distribution in the cross section was experimentally obtained in the mid-IR range of the spectrum. Practical significance. The metasurface created in the course of this work, including the process of its design and manufacturing technology, may be of potential interest for use in free space optical communication based on mid-infrared quantum cascade lasers with multiplexing orthogonal spatial modes.
Статья, 2024
Рассмотрена возможность распознавания непрозрачных материалов удаленных объектов с помощью импуль... more Рассмотрена возможность распознавания непрозрачных материалов удаленных объектов с помощью импульсной лазерной фототермической радиометрии с длительным импульсным воздействием. Приводятся теоретические расчеты дальности распознавания материалов при лазерной активации их поверхности. Результаты расчета свидетельствуют о существенном влиянии тепловых параметров на дальность распознавания. Экспериментально показано, что имеет место уменьшение дальности примерно на порядок величины, если материал объекта поиска обладает большой тепловой инерцией (металлы) по сравнению с материалом с малой тепловой инерцией (поликарбонатом, резиной), что обеспечивает достаточную вероятность для их различия. При этом на длине волны лазерного излучения должно выполняться условие сильного поверхностного поглощения. В случае синтетических полимерных продуктов в наибольшей степени этому удовлетворяет СО2-лазер. Влияние ветровой нагрузки на температуру лазерного пятна на объекте является одним
из ключевых в рассматриваемом методе. Предлагается способ сведения к минимуму этого влияния и даже его практически полного устранения. Обсуждаются вопросы, связанные с возможностью
увеличения дальности распознавания.
Article, 2024
The feasibility of recognizing opaque materials in remote objects using pulsed laser photothermal... more The feasibility of recognizing opaque materials in remote objects using pulsed laser photothermal radiometry with prolonged pulsed exposure is examined. Theoretical calculations are given of the range of recognition of materials with laser activation of their surfaces. The computational results indicate a signifi cant infl uence of thermal parameters on recognition range. It is shown experimentally that there is a reduction in the range by roughly an order of magnitude if the material of the search object has a large thermal inertia (metals) compared to a material with a low thermal inertia (polycarbonate, rubber), which provides a suffi cient probability for their diff erence. Here a condition of strong surface absorption must hold at the laser wavelength. In the case of synthetic polymer products these conditions are met to the greatest extent by a CO 2 laser. The eff ect of wind load on the temperature of a laser spot on the object is one of the key conditions in this method. A way of reducing this eff ect to a minimum or even eliminating it nearly completely is proposed. Issues related to the feasibility of increasing the recognition range are discussed.
Влияние поверхностного слоя на стойкость ниобаталития к действию лазерного излучения, 1977
Для доказательства существования поверхностного слоя в ниобате лития применена методика многократ... more Для доказательства существования поверхностного слоя в ниобате лития применена методика многократного нарушенного полного внутреннего отражения. Определены толщина и коэффициент поглощения поверхностного слоя. Показано, что при облучении поверхности ниобата лития допороговой плотностью энергии имеет место эффект накопления воздействия лазерного излучения на поверхность ниобата лития. В работе приведены зависимости порога разрушения поверхности ниобата лития от длительности лазерного импульса и диаметра фокального пятна. Результаты эксперимента по исследованию зависимости поверхностной стойкости от длительности импульса подтверждают наличие у ниобата лития поглощающего поверхностного слоя.
Statistics of laser damage to the surface of lithium niobate
Soviet Journal of Quantum Electronics
An analysis is made of the density of the distribution of the laser strength over the surface of ... more An analysis is made of the density of the distribution of the laser strength over the surface of lithium niobate. It is shown that distributions of this kind are polymodal due to the presence of defects of several different types with different damage thresholds. The distribution of the laser strength on the surface of one sample, representing defects of one
Journal of Applied Spectroscopy
The present work is devoted to the development o/ the method o/ laser photothermal radiometry wit... more The present work is devoted to the development o/ the method o/ laser photothermal radiometry with a view to im:reas~tg its spatial resolution over the depth o/ the specunen when sat/ace layers o/ th~ substance o/ thickness about I pm or less are to be investLgated. As an example, results o/ an int,estigath~n o/ radL~tion absorption in the sur/ace layer o/ a ~th~m n~a t e crystal are presented. The absorption index measured at a wm,elen~ o/1.08 pm was-0.6 cm-I.
Bulletin of the Russian Academy of Sciences Physics
Journal of Molecular Structure: THEOCHEM, 1999
Molecular graph invariants are often used as molecular descriptors in 'structure-property' correl... more Molecular graph invariants are often used as molecular descriptors in 'structure-property' correlations. There exists an infinite number of graph invariants. Most of them are constructed using refined mathematical operations with graphs and cannot be easily interpreted in structural or physico-chemical terms. So, the problem of the choice of molecular descriptors in 'structure-property' correlation appears. It is known that many invariants are related to each other by strict or approximate formulas. Thus, these descriptors reflect the same features of molecular structures. So, the following problem appears: for any finite set of molecular (or arbitrarily labeled) graphs, to find a finite set of basis invariants, such that any invariant of these graphs could be uniquely expressed as a linear combination of basis invariants. A solution of the above-mentioned problem and some examples are presented in the given paper.
<title>Investigation of the possibility of noncontact obtaining mode-selection elements of gas laser cavity</title>
LAMILADIS '91 Intl Workshop: Laser Microtechnology and Laser Diagnostics of Surfaces, 1992
ABSTRACT At present, the intracavity diaphragming method is usually used for the selection of tra... more ABSTRACT At present, the intracavity diaphragming method is usually used for the selection of transverse modes of gas laser cavity with a hard diaphragm being placed inside the cavity. Its position and size are determined theoretically. Narrowing of the working canal of a gas-discharge tube to the necessary dimension may also be used as a diaphragm. The above selection method has a number of disadvantages, essentially affecting manufacture of the device and its parameters. The aim of this work is to investigate the possibility of transverse mode selection in a gas laser cavity with methods of laser technology. This approach to selection mode problem differs from previously known ones in that the selection process takes place in the assembled emitter.
Quantum Electronics, 2011
Laser methods of standoff detection of explosive traces on surfaces of objects are considered. Th... more Laser methods of standoff detection of explosive traces on surfaces of objects are considered. These methods are based on active formation of multi-and hyperspectral images of an object examined. The possibilities of these methods and the prospects of their development are discussed. Emphasis is laid on the justification of the most preferred field of application of the technique under consideration.
Measurement of the body surface temperature by the method of laser photothermal radiometry
Quantum Electronics, 2003
The specific features of contactless measurements of the body surface temperature by the method o... more The specific features of contactless measurements of the body surface temperature by the method of repetitively pulsed laser photothermal radiometry are considered and the requirements to the parameters of the laser and measurement scheme are formulated. The sensitivity of the method is estimated. The advantages of laser photothermal radiometry over the conventional passive radiometric method are discussed. Bibtex entry for
Quantum Electronics, 2008
The application of the method of modiéed laser photothermal radiometry for studying the photoindu... more The application of the method of modiéed laser photothermal radiometry for studying the photoinduced absorption in thin élms is considered. The sensitivity of the method is estimated. The mechanism of induced near-IR absorption in titanium dioxide élms is proposed and the nature of surface defects responsible for this process is explained. It is shown that kinetic equations describing monomolecular recombination are consistent with the experimental dependences for the thermal activation energy of defects equal to 0:17 AE 0:04 eV.
Recent Patents on Engineering, 2009
The knowledge of photoinduced absorption spectrum gives important information about the material ... more The knowledge of photoinduced absorption spectrum gives important information about the material defect structure, which largely determines its properties and practical application. This article reviews the developments and patent literature in the area of photothermal methods modified for measurement steady state and temporal behavior of light-induced (photoinduced) absorption in bulk materials and thin films. These noncontact methods are characterized with high sensitivity, temporal and spatial resolution and successfully expand traditional techniques. A number of various schemes of photothermal methods were modified for light-induced absorption measurement where compared. Every item has its advantages as well as disadvantages. The results of analysis show that existing photothermal technique is a promising solution to meet the size, simplicity of operation, inexpensiveness, possibilities, and cost requirements of this technique.
PHOTONICS RUSSIA, 2021
The article shows the possibilities of nondestructive testing of the subsurface structure of vari... more The article shows the possibilities of nondestructive testing of the subsurface structure of various objects by means of pulse thermography technique. A number of examples are presented and their structure is analyzed. The technique includes heating the surface of an object with laser radiation and pyrometric investigation of local changes in surface temperature. Information is extracted from thermography results obtained both during forced heating and during subsequent cooling of the sample. The main attention in the article is paid to parts made of plastics used as structural materials in a wide range of products.
Pulse laser thermography as a non-destructive method of latent surface defects of materials
IOP Conference Series: Materials Science and Engineering
The time dependences of the surface temperature increment of painted metal objects were studied d... more The time dependences of the surface temperature increment of painted metal objects were studied depending on the thickness of the layer subjected to corrosion, as well as putty, restoring erosion defects on it. Hidden under a layer of paint, they cannot be detected remotely during normal visual observation. At the same time they are well detected by pulsed laser thermography. The experimental data in the work are compared with the results of mathematical modeling. Particular attention is paid to eliminating possible distortions caused by external contamination of the tested objects. 1. Introduction Remote detection of latent defects on the surface of materials based on active photothermal radiometry (thermography) is a very attractive technology, the beginning of which was laid in the late 70s-early 80s of the last century [1-4]. Over the years, this technology has undergone significant development. In the broad sense of the word, one can speak of flash thermography [5, 6] and modulation (lock-in) IR thermography [7, 8]. In this case pulsed, or non-stationary, thermography is the most common form of non-destructive assessment of the object of study using the thermographic method (NDE, nondestructive evaluation) [9-13]. This is due to the possibility of studying significant areas on the surface of the object in the presence of a high-speed IR camera with a large field of view, which is of fundamental importance for increasing the productivity of non-destructive testing of materials. Therefore, the main attention in the future will be given to the possibilities and development of this particular type of material research. The physical principle underlying the use of flash thermography for non-destructive testing is to measure the time dependence of surface temperature changes, while lock-in thermography allows you to study the phase of the photothermal signal. In both cases, the difference in thermal diffusion in different places of the sample due to the presence of defects and inhomogeneities in it affects the measurement result. In other words, subsurface defects change the rate of thermal diffusion, thereby manifesting itself in a change in the parameters of the recorded photothermal signal in the places where defects exist relative to areas where they are absent. Any inhomogeneities, such as inclusions, subsurface defects, or porous formations distort the propagation of thermal waves and modify the temperature response on the surface of the sample in comparison with the defect-free region. Due to the direct relationship between the thermal and mechanical properties, the detection of the distribution of the thermal signal allows mapping of the physical properties of the material under study during its scanning.
Quantum-Cascade Lasers in Medicine and Biology (Review)
Journal of Applied Spectroscopy
The problems of application of quantum-cascade lasers (QCLs) in biomedical practice are considere... more The problems of application of quantum-cascade lasers (QCLs) in biomedical practice are considered. A comparative analysis of laser spectroscopy methods for non-invasive diagnostics of diseases by exhaled air has been carried out; examples of the practical implementation of this idea based on QCL are given. The use of QCL in traditional laser surgery and laser angioplasty is discussed. Particular attention is paid to the consideration of terahertz imaging of soft tissues, as well as to the issues of microspectroscopy and the creation with its help of hyperspectral images of biological tissue in the middle infrared range. A number of problems associated with the use of QCL in medicine have been formulated, and possible directions for promising research, where QCL can play a decisive role, are indicated.
Soviet Journal of Quantum Electronics
An investigation of the temperature dependence of the optical strength of TiO2 coatings in atmosp... more An investigation of the temperature dependence of the optical strength of TiO2 coatings in atmospheres consisting of various gases demonstrated that the water adsorption processes had a decisive influence on the optical strength of TiO2 at λ = 1.06 µ. A model of laser damage was proposed to explain not only the results obtained, but also some of the known
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Papers by Leonid Skvortsov
из ключевых в рассматриваемом методе. Предлагается способ сведения к минимуму этого влияния и даже его практически полного устранения. Обсуждаются вопросы, связанные с возможностью
увеличения дальности распознавания.
из ключевых в рассматриваемом методе. Предлагается способ сведения к минимуму этого влияния и даже его практически полного устранения. Обсуждаются вопросы, связанные с возможностью
увеличения дальности распознавания.
The most promising method of countering infrared seeker and RSTA with two-dimensional multispectral photodetector arrays (FPA) is considered their functional dazzling continuous or pulsed laser radiation whose wavelength falls into the FPA sensitivity [1,2].
The paper provides a rationale for the possibility of using quantum cascade laser (QCL) mid-infrared spectral range for functional suppression systems that are sensitive in this spectral region.
[1] R.Schleijpen, J.Heuvel, A.Mieremet, B.Mellier, F.Putten, Proc. SPIE 6543, 65431B (2007).
[2] C.Willers, M.Willers, Proc. of SPIE 8543, 85430M-1 (2012)