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1V.E. Zuev Institute of Atmospheric Optics of the Siberian Branch of the RAS (Russian Federation) 2Institute of High Current Electronics (Russian Federation)
This PDF file contains the front matter associated with SPIE Proceedings Volume 10614 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
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In the present paper we present the results of a comparative analysis of pulsed copper vapour lasers with visible emission wavelengths of 510.6 and 578.2 nm and pulse duration of 10-30 ns and known types of technological lasers as well as the prospects for using the copper vapor laser for microprocessing of materials.
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This work describes an experimental study of obtaining the amplified spontaneous emission (ASE) on sodium D-lines using nonresonance broadband optical pumping. ASE is observed at transitions D2 and D1 line: 589 nm (32 P3/2 – 32 S1/2) and 589.6 nm (32 P1/2 – 32 S1/2). The active medium was pumped by the dye laser with FWHM of 5 nm, maximum radiation in the range 584.5-586.5 nm, and pulse energy above 2 mJ. The working temperature of the active medium was 260 °С, initial pressure of buffer gas-helium was 300 torr (operating pressure - 500 torr). A change in the absorption spectra at D lines at different temperatures of the active medium and buffer gas pressures was observed
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Investigation of the energy characteristics of copper, manganese, lead halide vapor lasers with inner reactor and small active volume 90 cm3 was made. The optimal operating pulse repetition rates, temperatures, and buffer gas pressure for gas discharge tubes with internal and external electrodes are determined. Under identical pump conditions, such systems are not inferior in their characteristics to standard metal halide vapor lasers. It is shown that the use of a zeolite halogen generator provides lifetime laser operation.
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We present new results on numerical investigation of characteristics of pulse-periodic inductive copper vapour lasers. In these lasers pump pulses are trains of high-frequency (~ 30 MHz) current oscillations repeated at a frequency of 2-17 kHz. An inductive laser with an annular working volume of 1.7 l was considered and its possible output parameters were studied. We analyze specific features of working medium excitation in an HF-discharge; diversity of the obtained laser pulse shapes and possible applications are discussed as well.
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The results of studies on the formation of a volume discharge in an electric-discharge XeCl laser with a maximum specific pumping power of 4.7 MW/cm3 are presented. It is shown that with a half-cycle duration of discharge current of 20 ns, the radiation pulse duration on the base is 100 ns. A good agreement between the experimental and numerical results obtained with the XeCl laser was demonstrated. Plasma-chemical processes occurring in a volume discharge at a maximum electron concentration in the plasma of ~ 7×1015 cm-3 are considered.
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The results of examination of characteristics of a CuBr laser with small active volume operated in the doublepumping-pulse mode with a lasing pulse repetition rate of 50 Hz are presented. Owing to the use of pumping sources with pulsed step charge of the working capacity, effective energy input to the active medium of the laser is realized. The potential to enhance the laser efficiency by choosing the optimum voltages of dissociation and excitation pulses and time delay values is discussed. It is confirmed that a more than twofold increase in the laser efficiency may be achieved through optimization and matched injection of the excitation-pulse energy into the active medium plasma. The maximum efficiency of the laser was 2.7%.
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Colloidal solutions of Ag silver nanoparticles were studied in the presence of Eu3+ ions and in the absence of their. Silver nanoparticles were created by the method of green synthesis using an aqueous solution of mint. Optical and electronic spectroscopy have been used to explore the interaction of these ions with silver nanoparticles.
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The main approximations for calculation of effective parameters of inhomogeneous media are Bruggeman effective medium approximation and Maxwell Garnett model, which are currently widely used in the description of composites containing various nanostructured objects. In this paper we consider a simple approach to these approximations, allowing to embrace the most general case of statistically anisotropic media with particles of arbitrary internal structure, and also to clarify their physical meaning. The type of result essentially depends on the choice of "effective cells" used in estimating the field and induction values averaged over the volume.
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The interaction of humic acids (HA) isolated from oxidized and brown coals with copper, nickel, and cadmium ions is investigated. The complexation constant of HA with heavy metal ions is determined using the fluorescence quenching method. It is shown that preliminary mechanic activation of humic-containing substances increases the binding coefficients of HA with copper and nickel ions in 1.5 to 3.5 times, as compared to cadmium ions, for which the values of the fluorescence quenching constant КSV decrease. This is due not only to structural changes in HA after the mechanic activation, but also to the nature of metal ions.
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Polyvinylchloride films were obtained and studied by optical methods after thermolysis. A strong increase in the intensities of the absorption spectra and a shift in the long-wave region with increasing thermolysis time are established. These facts can be explained by the increase in the number and size of the conjugated carbon double bonds. The optical absorption method is sufficiently informative to determine the relative change in the number of conjugated carbon double bonds and their sizes. The amount of conjugated carbon double bonds in polyvinylchloride films is estimated as a function of the thermolysis time. The shift of the absorption spectra to a longer-wavelength region is analyzed with increasing conjugated carbon double bonds with increasing thermolysis time studied.
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By the method of green synthesis, silver nanoparticles were obtained in colloidal solutions. The solutions were modified with thulium ions. Using the method of electron microscopy and optical method, the properties of silver nanoparticles obtained are studied. The influence of change in concentration of the solution of mint and thulium ions on the properties of colloidal silver nanoparticles was studied.
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Recently, research has been developing on nanoscale objects (a group of atoms) for which the concept of dielectric constant has a conventional meaning and therefore requires refinement and even analysis. In this paper we analyze the change in the intensity of Raman scattering of nanoobjects placed on a flat substrate. Some variants were shown for which the scattering can vary by more than an order of magnitude. In particular, on an ideal metal substrate, the region of antinode of a standing light wave upon reflection does not extend to the near-surface layer in which the nanoobject is located. And for this reason the Raman scattering decreases by more than an order of magnitude. Conditions are shown under which a decrease in Raman scattering from nanoobjects can be compensated and even increased.
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We used high adsorption properties of the cationic biopolymer chitosan to synthesize colloidal polymer particles (average size about 0.3 μm) with immobilized CdTe quantum dots (QDs) and organic dye (erythrosin B). A high local concentration of fluorophores bound to the particles (about 10–3 M), as well as a wide overlap of their optical spectra result in an efficient (up to 80%) Förster resonance energy transfer (FRET) from QDs ensembles to dye molecules. The FRET was registered by both steady-state (quenching of the donor and enhancement of the acceptor fluorescence) and time-resolved methods (decreasing of donor lifetime). The dependence of the transfer efficiency on acceptor concentration was analyzed within the scope of the Förster theory extended for the case of multiple energy transfer configuration. The average distances between the donor and acceptor as well as local concentration of fluorophores within particles were determined. It was demonstrated that the synthesized particles can be used as FRET-based sensitive probes for inter-fluorophore distance calculation within the range of 4 ÷ 9 nm.
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Spectroscopy and photochemistry of humic acids are discussed. The samples of HAs fractions were obtained from Fluka Chemical Co and prepared from peat of Western Siberia region. The comparative analysis of these acids with the sample of humic acids allocated from brown coal is carried out. A specific feature of the reactor is the use of barrier discharge excilamp (KrCl) with radiation wavelength λ = 222 nm. Influence of the received humic acids on process of photodegradation of herbicide - 2.4-dichlorophenoxyacetic acid is considered.
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The transverse structure formation processes of a laser beam after multiple filamentation were investigated. It is shown that the spectra of post-filamentation light channels (PFC), rings and beam differ substantially. The spectrum of PFC has a significant and symmetrical spectral broadening and covers a range of 600-1100 nm. The broadening of the spectrum of the rings is asymmetric and is directed mainly to the short-wavelength region of the spectrum. The broadening data are stable and do not change when moving away from the multiple filamentation zone. The annular structure of radiation in the cross section of the beam is formed around individual filaments within the region of multiple filamentation, and at a distance of tens of meters from it begins to form a common ring structure surrounding postfilamentation channels.
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The study of structural properties of nanocomposites, based on different types of single walled carbon nanotubes (SWCNTs) and proteins (albumin, collagen), was carried out. The binding of protein molecules to the carbon component was described by Raman spectroscopy. Complex analysis of the structure and microporosity of nanocomposites was performed by the X-ray microtomography. The nanoporosity study was carried out using the low-temperature nitrogen porosimetry method. Samples based on SWCNTs with smaller size had the most homogeneity. With an increase in the concentration from 0.01 to 0.1 %, the mean micropore size increased from 45 to 93 μm, porosity in general increased from 16 to 28 %. The percentage of open pores was the same for all samples and was 0.02. As it was shown by Raman spectroscopy the protein component in nanocomposites has undergone irreversible denaturation and can act as a biocompatible binder and serve as a source of amino acids for biological tissues. These nanocomposites are bioresorbable and can be used to repair cartilage and bone tissue. This is especially important in the treatment of diseases of hyaline cartilage and subchondral bone.
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Optical absorption spectra in the temperature range of 85-300 K and IR absorption spectra at room temperature of four diamond samples were studied. All samples demonstrated the GR1 vibronic system of a neutral vacancy. The absorption coefficient at the zero-phonon line at 1.673 eV decreased by the power law in the temperature range of 120-230 K. Outside this temperature range, the absorption on the neutral vacancy did not practically changed. The value of the absorption coefficient at the neutral vacancy correlated well with the densities of nitrogen impurity-defective NV-, N2Vand N4V-complexes.
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The low-frequency acoustic mode in nanoparticles of different nature in aqueous suspension has been studied by stimulated low-frequency Raman scattering (SLFRS). Nanoparticles investigated (CuO, Ag, Au, ZnS) had different dimensions and different vibrational properties. Synthesis of cupric oxide nanoparticles in acoustoplasma discharge is described in details. SLFRS has been excited by nanosecond pulses of ruby laser. Spectra of the scattered light had been registered with the help of Fabry-Perot interferometer. SLFRS conversion efficiency, threshold and frequency shift of the scattered light are measured.
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The experimental setup for determination of particle sizes by nanotracking is developed. It is shown the possibility to identify particles with different fluorescent labels using developed experimental setup. The first results of analysis for samples of polystyrene micro- and nanoparticles are obtained using developed experimental setup.
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The effect of iron (III) oxide nanoparticles produced in acoustoplasma discharge with cavitation on the concentration and the sizes of particles in model protein solutions, human blood serum and plasma samples is studied. Dynamic and static light scattering data on size and concentration of particles show that the nanoparticles addition to fibrinogen-thrombin system affects the course of enzymatic reaction. Interaction of nanoparticles with fibrinogen solution (before thrombin addition) does not significantly change the distribution of scattered light intensity on particle sizes. Comparison of the relations of particle sizes and their concentration for fibrinogen solution with and without nanoparticles shows an increase of the slope of size-concentration relation in a log-log scale, which indicates an increase in the concentration of small particles and decrease of big ones. For model solution of fibrinogen with thrombin, initially incubated with iron oxide nanoparticles, the slopes of the size-concentration relation equals to k = –(4.62±0.33) and slightly differs from the slope of the relation for fibrinogen-thrombin system without nanoparticles k=–(4.23±0.28). We believe that changes in the size-concentration relation indicate the interaction of nanoparticles with proteins, which results in gelation rate change.
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Luminescence of nanomaterials in green-blue range, anti-Stokes with respect to the exciting ruby laser pulses, is studied at different temperatures. Both high-ordered systems and random materials have been used as samples. Spectral and temporal characteristics of the luminescence have been measured. Two types of temporal behavior have been found out depend on temperature. Long luminescence (up to few seconds) under nanosecond excitation has been shown to exist only at the temperatures below the definite threshold, which was found to be 110 K.
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The effect of the tungsten coating on the photoelectric and electrophysical properties of electron-silicon samples after gold diffusion was analyzed. The trap levels associated with tungsten atoms, with a tungsten complex + vacancy, and with an oxygen + vacancy complex were detected. In samples of silicon doped with gold, both with and without a tungsten coating, the resistivity increased by 2-3 orders of magnitude, which indicates the creation of additional energy centers associated with gold and gold complexes caused by tungsten. At the same time, the time of nonstationary relaxation photoconductivity has greatly decreased, which also indicates the creation of additional recombination centers and trap levels.
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The problems of through laser cutting of sodium silicate glasses by laser-controlled thermal cleavage are considered. A wide variety of obtained end face shapes is demonstrated. It is shown that the strength of glass samples cut by the laser is about two times higher than that of samples cut by a glass cutter.
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The task that faced the authors was construction of a mobile lidar complex for detection and investigation of aerosol-gas formations in the atmosphere. The complex must be constructed of commercial industrially produced components as much as possible. Many of engineering solutions had been previously worked out by the authors when the first lidar of such type was developed. The complex is designed for study of capabilities of lidar sensing for remote investigation of aerosol-gas formations by their fluorescence and Raman scattering spectra, as well as topographyc objects by fluorescence spectra of their surfaces. The complex has been tested in 2016, and may be applied for atmospheric sensing, for detection of potentially hazardous and dangerous admixtures above the cities, industrial and agricultural emissions, including emissions after disclosures of agricultural animal burial sites. The complex is mounted on a motor vehicle chassis and is energy-independent, and that allow using it for remote sensing of different objects in different natural conditions. Probing distance: 30 000 meters in elastic scattering channel and 5 000 meters in fluorescence channel.
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In the paper a simple spectral unit designed for excitation and registration of luminescence spectra of natural objects is described. The unit is composed of two basic systems: an excitation system and a registration system. Either x-ray or laser emission can be used for luminescence excitation. The registration system is based on lattice monochromator. The studied object is placed directly at the monochromator entrance slit. Two lead plates are located inside the monochromator case. They protect photodetector that is located behind the monochromator exit slit from x-ray radiation. When emission is decomposed by the diffraction grating, spectrum aliasing occurs, which can be eliminated using optical filters. The diffraction grating rotation is controlled by a computer. Manual control of the rotation angle is also provided. The PMT signal, amplified by dc amplifier, goes to analog-digital converter (ADC). Digitized ADC signal goes to COM port of the computer. Spectrum projection is displayed on the screen and can be recorded to computer’s memory. Switching of analog devises to the dc amplifier output is provided. Examples of processing of the experimental results, obtained using the abovementioned unit, are presented in the paper.
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Measurements of the diffuse reflection coefficients of organic and inorganic materials and media in solid, granular and liquid forms were made in the UV field of 230-400 nm. A single channel spectrometer with an integrating sphere was used. Relation between diffuse reflection coefficients and the structure and composition of the samples is discussed. These data allow us to estimate the prospect of machine vision systems application for the UV range in such areas as biology, geology, remote control of materials and media.
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The stabilization system implemented has allowed one to achieve phase residual instability ~0.17 radian (rms) for the 30 fs-pulse, which is sufficient for nonlinear interaction radiation with optical medium in forthcoming lightwave electronics experiments.
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Numerical modelling of selective heating of skin vessel with copper vapor laser (CVL) was applied to determine both the depth of the vessel location and diameter of vessels targeted for selective and safe coagulation by means of the laser irradiation
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Photochemical properties of carbohydrates, including mono- and polysaccharides, as well as various kinds of glycoproteins, proteoglycans, and glycolipids, take great attention last decades due to their significance for clarifying physical and chemical processes happening in biological molecules under irradiation. Understanding of excitation and ionization processes is important for interpretation of mass spectrometric (MS) experiments, which is the main instrument for quick and reliable analysis of biological samples. While polynucleotides and simple proteins can be easily studied by standard MS techniques (MALDI, ESI, and CID), carbohydrates and complicated biomolecules containing oligosaccharide residues are difficult to be ionized. Carbohydrates give a low signal yield. Their detection and analysis requires the special equipment and technology. Therefore, the development of new efficient methods for identification of carbohydrates in biological samples currently is the critical scientific and technical problem. In this work we study dissociation processes taking place in potassiated α- and β-glucose, which can be concerned as the modelling molecule for investigation of wide range of carbohydrates and carbohydrate fragments of biomolecules containing potassium ion as the ionization source. Here we compare deionization process with H2O and KOH elimination channels, as far as their competition with cross-ring dissociation processes. Potential energy surface were optimized by the density functional B3LYP/6-31G* method. Single point energy calculations in minima and transition state points were performed by G3(MP2,CCSD) ab initio method.
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Experimental study and theoretical analysis of growth of microstructures (microtowers) on liquid metals by fs laser pulses have been carried out. Theoretical analysis has been performed on the basis of the two-temperature model. Compared to ns laser pulses, in fs irradiation regimes the heat-affected zone is strongly localized resulting in much larger temperatures and temperature gradients. In the experimental irradiation regimes, the surface temperature of liquid metals studied may reach or even exceed a critical level that culminates in phase explosion or direct atomization of a metal surface layer. However, before explosive ablation starts, a stress wave with an amplitude up to several GPa is formed which demolishes oxide covering. Moreover, at high laser fluences laser-induced breakdown is developed in oxide layer covering the metal surface that leads to destruction/ablation of oxide without damaging metal underneath. An overall scenario of microstructure growth with fs laser pulses is similar to that obtained for ns irradiation regimes though the growth threshold is lower due to smaller heat-conduction losses. Also we managed to obtain microstructures formation by the action of spark discharge.
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The cathodoluminescence spectra of nine diamond samples at temperatures of 82-295 K were investigated. According to the presence of the N3a vibronic system with the zero-phonon line at 2.68 eV in the luminescence spectra, six samples were identified as natural. By the presence in the luminescence spectra of the 2.56-eV vibronic system and the unstructured band at 2.54 eV, associated with nickel, two samples were identified as synthetic, grown at high pressure and high temperature. Due to exciton luminescence at 5.271 eV and the absence of any spectral features of impurity nature, one sample was identified as synthetic, grown by the chemical vapor deposition. Based on the data obtained, the technique for identifying of natural and synthetic diamonds has been proposed.
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V. I. Krasovskii, I. N. Feofanov, S. I. Rasmagin, D. A. Zadorin, R. A. Zakharyan, M. A. Kazaryan, L. L. Chaikov, N. A. Bulychev, A. S. Averyushkin, et al.
Proceedings Volume International Conference on Atomic and Molecular Pulsed Lasers XIII, 106140Z (2018) https://doi.org/10.1117/12.2303414
The nonlinear response of metal oxide nanoparticles obtained by the acoustic plasma method is measured in aqueous disperse systems at a wavelength of 532 nm. Induced absorption is detected in the Cu2O, WO3 and ZnO disperse systems, and bleaching is detected in the Fe2O3 system. The real and imaginary parts of nonlinear third-order susceptibilities are determined.
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Transmission spectra of holographic sensors based on the Denisyuk holograms with silver nanograins embedded in the polymer matrix are investigated. It is necessary for the determination of the operation mode and of optical parameters of the sensors. The spectra have a narrow Bragg dip against a background decreasing with decreasing the wavelength. Three parameters of this dip determine the operating mode of the sensor. To calculate them, it is necessary to know 3 background parameters. All the parameters are calculated from fitting curves based on the formula proposed earlier which approximates the experimental spectrum quite well. It turns out that the spectral interval chosen for fitting is important and a solution exists not over any interval. When it exists, the parameters of the dip (the main goal of our work) are determined with a good accuracy. As for the optical parameters of the background, those associated with light scattering and with absorption seem to be strongly related. Changing the fitting interval leads to a correlated change of the values of parameters, sometimes considerably. Nevertheless, the fitting function approximates the experimental spectrum quite well and the accuracy of determining the Bragg dip is high.
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The paper shows, that a low-temperature plasma initiated in liquid media in interelectrode discharge gap is able to decompose hydrogen containing organic molecules resulting in obtaining gaseous products with volume part of hydrogen higher than 90% (up to gas chromatography data). Tentative assessments of energy efficiency, calculated with regard for hydrogen and feedstock heating value and energy consumption, have shown efficiency factor of 60-70%, depending on the source mixture composition. Theoretical model calculations of discharge current and voltage have been performed; the values are in good accordance with experimental data.
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Nanoparticles of tungsten, copper, iron, and zinc oxides were synthesized in acoustoplasma discharge. Their size distribution was studied by electron microscopy and laser correlation spectroscopy. Ultrasound was found to narrow significantly the size distribution width of zinc oxide nanoparticles. Water suspensions of zinc oxide nanoparticles showed photoluminescence in red and near infrared spectral ranges, which makes them a promising material for luminescent diagnostics of biological systems.
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In this paper, differences in the luminescence intensity of nanoparticles of metal oxides synthesized in electric discharges in liquid media under the influence of intense ultrasonic vibrations prior to cavitation and after the start of cavitation regime have been studied. The increase in the luminescence intensity of nanoparticles obtained by ultrasonic cavitation can be explained by the formation of defects in oxide crystals under the influence of intense mechanical action. In the process of synthesis, the particles are exposed not only to the action of electromagnetic fields, but also to shock waves during the collapse of cavitation bubbles, which leads to the formation of defective valence structures and delocalization of electrons.
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The characteristics of electrical discharges in liquid media under the influence of intense ultrasonic vibrations are investigated and the difference in dynamic characteristics of discharges before cavitation and after cavitation begins. The experiments carried out during this work made it possible to establish that in a liquid in an intense ultrasonic field above the cavitation threshold there exists a special form of an electric discharge characterized by volumetric luminescence in the entire space between the electrodes and the current-voltage characteristic inherent in an anomalous glow discharge in a gas.
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The mechanism of mechanical ablation of nanoparticles during the interaction with a high-power laser radiation pulse is proposed. A particle is polarized under a laser electric field, and electric forces acting on field-induced oppositesign charges cause rupture stresses. Upon reaching the stresses exceeding the maximum allowable values for a given material, a nanoparticle decays into two ones. This effect can be used for narrowing the size distribution of nanoparticles produced by the laser ablation method.
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The possibility of the Gadolinium nuclei energy levels population inversion under neutron bombardment is theoretically shown. In the process two isotopes of gadolinium take part. Light isotope Gd155 capturing neutron transforms to heavy isotope Gd156 at that heavy nucleus is in an excited metastable state. The population inversion is investigating during several tens of second when the neutron flux intensity is 1013 cm-2 · s-1.
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Studying the processes occurring in biological systems under irradiation is critically important for understanding the principles of working of biological systems. One of the main problems, which stimulate interest to the processes of photo-induced excitation and ionization of biomolecules, is the necessity of their identification by various mass spectrometry (MS) methods. While simple analysis of small molecules became a standard MS technique long time ago, recognition of large molecules, especially carbohydrates, is still a difficult problem, and requires sophisticated techniques and complicated computer analysis. Due to the large variety of substances in the samples, as far as the complexity of the processes occurring after excitation/ionization of the molecules, the recognition efficiency of MS technique in terms of carbohydrates is still not high enough. Additional theoretical and experimental analysis of ionization and dissociation processes in various kinds of polysaccharides, beginning from the simplest ones, is necessary. In our work, we extent previous theoretical and experimental studies of saccharides, and concentrate our attention to protonated glucose. In this article we paid the most attention to the cross-ring dissociation and water loss reactions due to their importance for identification of various isomers of hydrocarbon molecules (for example, distinguish α- and β-glucose).
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The finite-element method was employed to model and simulate the terahertz (THz) wave propagation in a tapered waveguide. The relatively infrequent use of dielectric waveguides and antennas is due to the lack of analysis tools. Maxwell's equations have an analytical solution only for a rectangular shape crystal. Lack of analysis tools inhibits antenna development because physicist must resort to cut-and-try methods. It is only recently that simulation of electromagnetic fields in arbitrarily shaped media has become fast and practical.Numerical simulation results showed changes in the mode structure of the THz radiation along the length of the crystal, the concentration of the THz field inside the crystal and the radiation structure from the crystal-air interface. Excitation of ТHz radiation in the tapered waveguide with the help of an optical laser pulse permits the resolution of problems connected with input/output coupling - mode matching and single mode propagation. THz energy concentration by dielectric wedge antenna improves the spatial resolution and increases the signal/noise ratio (SNR) for the THz imaging and spectroscopy.
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To supress beam pointing instabilities after high power laser multipass amplifier with cryogenic closed-loop cooling the copper heatsinks were optimized. Active elements’ temperature dependency on diode pump regimes is measured. The alternative seed laser for the high power laser multipass amplifier with cryogenic closed-loop cooling was modeled and designed.
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L. G. Samsonova, K. M. Degtyarenko, R. M. Gadirov, A. V. Odod, T. N. Kopylova, A. Begimova, S. S. Krasnikova, I. K. Yakuschenko, S. Ya. Gadomsky, et al.
Proceedings Volume International Conference on Atomic and Molecular Pulsed Lasers XIII, 106141A (2018) https://doi.org/10.1117/12.2305575
The results of investigation of the luminescence under photo- and electroexcitation for four new compounds are presented. The spectral properties and photoluminescence are studied in ethanol, chloroform solutions and in films formed by thermovacuum deposition (TVD). The phosphorescence of compounds is investigated in ethanol at 77K temperature. The phosphorescence times of molecules are given. The electroluminescence is obtained in multilayered structure ITO/PEDOT/NPD/L /Ca/Al. It is shown, that spectral region of the photoluminescence of TVD films and electroluminescence coincide. Relations of electroluminescence efficiency with molecule structure, photoluminescence quantum yield and possibility of thermally activated delayed fluorescence are discussed.
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Optical radiation absorption in the poly-layer spherical microparticles simulating the inorganic/organic polyshell absorbing microcapsules is considered. With the aim of the finite-difference time-domain technique, the spatial distribution of the absorbed light power in microcapsules of various sizes and internal structure is numerically calculated. For the purpose of light absorption enhancement, we have engineered the optimal structure of a capsule consisting of a strong-refracting transparent outer coating and an absorbing layer which covers a liquid core. The proposed microcapsule prototype provides for a manifold increase in the absorbed light power density in comparison with the usual single-layer absorbing capsule. We show that for light-wavelengths-scaled microcapsules it is optimal to use a material with the refractive index larger than two as an outer shell, for example, titanium dioxide (TiO2). The highest values of the absorbed power density can be obtained in microcapsules with absorbing shell thickness of approximately a tenth of a laser wavelength. When laser radiation is scattered by a dimer constituted by two identical absorbing microcapsules the absorbed power density can be maximized by the choosing of proper dimer spatial configuration. In the case of strongly absorbing particles, the absorption maximum corresponds to a shift of the capsules to a distance of about their diameter, and in the case of weakly absorbing particles the absorption is maximal when particles are in geometrical shades of each other.
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We obtained the dispersion equations for calculating eigen values of the wave numbers of magnetic and electric discrete spectrum surface waves in bianisotropic gradient structure, as well as other basic parameters characterizing its waveguide properties. We researched an asymmetric planar waveguide, which central waveguide layer has special transverse dimensions and non-standard, but very important for applications in optics physical characteristics.
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The effect of astigmatism on laser air filamentation was studied numerically and experimentally. Limited supply of energy to the filament is shown to be the main feature of aberrational focusing, which facilitated the organization of quasi-solitons in the post-filament region. Quasi-solitons are realized due to the balance between linear diffraction and Kerr nonlinearity in the presence of background environment around zones with increased intensity. A highly directional SC of visible light is formed outside the visible filament zone in the resulting spatial quasi-solitons.
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Investigation of the destruction of 2,4-dichlorophenoxyacetic acid (2,4-D) under the influence of UV radiation from the KrCl excilamp with the use of additives of hydrogen peroxide, the Fenton reagent. Effective rate constants of degradation reactions of the initial compound were calculated. The estimation of efficiency of both each system separately, and together is given. The use of hydrogen peroxide additives and Fenton's reagent is due to the fact that the use of direct photolysis in some systems is ineffective. Addition of hydrogen peroxide in such cases increases the efficiency, due to the formation of active forms of oxygen in aqueous solutions. Thus, studies have been carried out to find the most effective amount of hydrogen peroxide additive and to create the most effective system for the destruction of chlorinated phenoxy acids when excited by a KrCl excilamp (222 nm).
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Mercury-free UV-radiation sources are described. An electron beam similar to cathode-ray tubes (CRT) excites a luminescent material in a vacuum bulb. A high density of excitation requires the cathode and the luminescent material to be resistant for that and provide the extended lifetime of the UV-radiation source. Carbon fibre and nano-carbon based field-emission cathodes produce long lasting stable emission with a high current density (up to 0.3-0.5 A/cm2 ). Li2B4O7:Cu and Li2B4O7:Ag luminescent ceramics survive under high radiation doses and provide UV luminescence bands peaked at 360-370 nm and 270 nm, respectively. The luminescence band at 360-370 nm has a good overlap with the fundamental absorption edge of TiO2, which is known as a photo-catalyst in air and water cleaning systems. The luminescence band at 270 nm overlaps with DNA absorption and provides a direct disinfection effect. We suggest the structure of complex luminescence centres and energy transfer mechanisms. The electron structure of lithium tetraborate and the contribution of impurities are also discussed in paper.
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Modern UV LEDs represent a potentially very advantageous alternative to thermal light sources, in particular xenon arc lamps, which are the most common light sources in trace gas-analyzers. So, the light-emitting diodes are very attractive for use of as light sources for Long Path Differential Optical Absorption Spectroscopy (DOAS) measurements of trace gases in the open atmosphere. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes have now allowed us to construct a portable, long path DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. First of all, we are talking about the measurement of sulphur dioxide, carbon disulphide and, oxides of chlorine and bromine. The parallel measurements of sulfur dioxide using a certified gas analyzer, were conducted and showed good correlation.
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The study of optical absorption of CVD diamond near the fundamental absorption edge was performed in the temperature range of 87-296 K. At temperatures lower than 195 K the absorption was practically constant. At higher temperatures the sharp increase of absorption took place. This sharp increase was attributed to the sharp enrichment of the phonon spectrum. Same phonon modes have different contributions to the negative and the positive branches of freeexciton absorption. For the negative branch (phonon absorption) the TA-mode dominated. For the positive branch (phonon emission) the TO-mode dominated. The possibility of diamond-based cathodoluminescent UV-sources at 235 nm was demonstrated.
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The decomposition products of atmospheric pressure plasma of repetitive pulsed discharge in apokamp and corona modes were determined by optical and chemical methods. It is shown, that the decomposition products contain mainly nitrogen oxides NOx. A brief review of the plasma- and thermochemical reactions in the pulsed discharges was made. The review and experimental data allow us to explain the reactive oxygen species formation mechanisms in a potential discharge channel with apokamp. The possible applications of this plasma source for treatment of seeds of agricultural crops are discussed.
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A parametric study of a system dedicated to non-coherent UV emission, by means of DBD excilamps, supplied by a controlled square shape current source is proposed. The presentation highlights on the one hand the performances experimentally obtained by combining together a set of 20 different bulbs with different diameters, gap and wall thicknesses (all the bulbs have the same length and are filled with the same Xe-Cl gas mixture), with different electrical power supplying conditions: magnitude, frequency (in the 30 kHz – 200 kHz range) and duty cycle of the square shape current pulses injected into the bulb. The performances concern the average UV power, the efficiency of the bulb conversion (electrical power to UV) and the adjustability of the power. On the second hand, we present design considerations of the power supply which has been especially developed for the purpose of these experiments.
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E. G. Batyrbekov, Yu. N. Gordienko, N. I. Barsukov, Yu. V. Ponkratov, T. V. Kulsartov, M. U. Khassenov, Zh. A. Zaurbekova, Ye. Yu. Tulubayev, K. K. Samarkhanov
Proceedings Volume International Conference on Atomic and Molecular Pulsed Lasers XIII, 106141K (2018) https://doi.org/10.1117/12.2303578
The spectral studies of optical radiation of gaseous mixtures are of interest for solving problems associated with finding gaseous media with high energy conversion efficiency of nuclear reactions into the energy of laser or spontaneous emission [1, 2]. Such media can be used to extract energy from nuclear and fusion reactors in the form of optical radiation, and also to control and adjust the nuclear reactors parameters. This paper presents the preliminary results of the reactor experiments to study the spectral-luminescent properties of gas mixtures (based on He, Ne and Kr noble gases) excited by the products of 6Li(n,α)3H nuclear reaction at different levels of the stationary power of the IVG.1M reactor.
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The spectral characters and increments of stimulated Rayleigh scattering in pure liquids and suspensions of Ag nanoparticles in toluene and hexane of principally different nature were investigated in this work. The correlation of two photon absorption spectra and stimulated scattering efficiency were discovered and analyzed. It is shown experimentally that the frequency shift of the scattered signal relative to the pump frequency greatly exceeds the theoretical value.
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Temperature transition processes in optical-acoustic deflectors are experimentally investigated. The spectral dependence of the scanning angles of the deflector depending on the frequency of the operating signal during the changes in the device temperature is studied. It is shown that the angle of diffraction changes as the temperature of the deflector increases.
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Here we present research data demonstrating how crop seeds response to ultraviolet produced by a barrier-discharge XeCl* excilamp with a wavelength of 290–320 nm (82–88 %). The data show that presowing ultraviolet treatment is stimulatory to seed germination and plant growth. Ultraviolet treatment increases the seed germinability by 20–30 % and the plant fresh weight by 54 %, compared to untreated control samples, and provides a developed root system with long twisted segments. The research results are encouraging for upgrading the UV technology to larger-scale seed irradiation.
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Creation of limiters for intensive laser radiation requires the development of effective methods for testing materials to determine the nonlinear optical parameters characterizing their properties. The limiting threshold, linear and nonlinear absorption coefficients can be determined not only from data of Z-scan with open aperture, but also with the help of a fixed location of the limiter. The use of this method makes it possible to determine the output characteristic of the studied material from which nonlinear optical parameters can be calculated. Characteristics of carbon nanotubes and graphene oxide in water were obtained with the fixed location of the limiter. The experiments were performed using an Nd:YAG laser that generates pulses of 16 ns duration at a wavelength of 532 nm with the linearly polarized laser beam in the horizontal plane and a shape closed to Gaussian type. Theoretical curves for method of fixed location of the sample according to threshold model was calculated and compared with the experimental data. Normalized weakening coefficients, limiting threshold, linear and nonlinear absorption coefficients were found for studied dispersions and calculation of Z-scan with open aperture was made. The value of normalized weakening coefficient was higher in dispersed medium of SWСNTs with water (Knorm≈20) in comparison with oxide graphene in water (Knorm≈14). The dependences of normalized weakening coefficient bias input energy were approximately linear in both cases.
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This work is devoted to the development of the approach to restoration of the spatial-temporal distribution of electric field in the human brain. This field was estimated from the model derived from the Maxwell’s equations with boundary conditions corresponding to electric potentials at the EEG electrodes, which are located on the surface of the head according to the standard “10-20” scheme. The MRI data were used for calculation of the spatial distribution of the electrical conductivity of biotissues in the human brain. The study of the electric field distribution using our approach was carried out for the healthy child and the child with autism. The research was carried out using the equipment of the Tomsk Regional Common Use Center of Tomsk State University.
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In our study we used rank-order filter, the emissions filter on the base of the criteria of Pearson, Gaussian filter and median filterfor improving the is fluorescence lifetime imaging microscopy (FLIM) data. The data obtained with the FLIM technology are the distribution with a pronounced peak, while during measurement the peak value is measured with an error. According to the analysisthe Gaussian filter is more useful to improve quality of FLIM data.Spatial filtering allows to reduce the noise component, obtained in the course of measurements, including reduction the influence of the individual bursts. Filtering in time scale allows to determine a peak value of intensity more accurately.This research was carried out using the equipment of Tomsk Regional Common Use Center of Tomsk State University.
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Nanoconstructions of gold nanoparticles (NPs) obtained via pulsed laser ablation in liquid with DNA-aptamer specific to protein tumor marker were visualized on the surface of screen-printed electrode using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). AuNPs/aptamer nanoconstuctions distribution on the solid surface was studied. More uniform coverage of the carbon electrode surface with the nanoconstuctions was showed in comparison with DNA-aptamer alone on the golden electrode surface. Targeted binding of the tumor marker molecules with the AuNPs/DNA-aptamer nanoconstuctions was approved.
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The mechanisms of the effect of vacuum ultraviolet (VUV) radiation (λ = 172 nm) on various types of microfungi spores were investigated. It is found that there are several parallel direct and indirect mechanisms, which lead to spores inactivation, including destruction of the cell wall and DNA by means of direct absorption of VUV radiation and by VUV photolysis reactive products. IR transmission spectra indicate the etching of the spore cell wall material with the predominant degradation of the polysaccharides. Electrophoresis of irradiated spores DNA shows heavy (about 20 000 pairs of nucleotides) and light fragments appearance. Experiments using an antioxidant (iodine) indicate the participation of reactive radicals in inactivation, which provide not less than 10% of inactivated cells
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Absorption spectra of paraffin-embedded prostate cancer and healthy tissues have been measured in the 0.2-3 THz range. The Principal Component Analysis and the Support Vector Machine (SVM) were applied to analyze experimental data. The SVM classifier was created which allows to distinguish the healthy tissues from tumor tissues, including classification of tumor tissue stage according to the Gleason scale.
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The results of the development of the Marx generator intended to supply an electron accelerator with the electron beam extraction into gas through a foil window are presented. The generator has air insulation and consists of 4-6 stages, assembled in the form of artificial long lines with the wave impedance of ~4 Ω. To eliminate reflections, each of the lines is provided with a matched load. Connection of both the stages in series and matched loads to the stages is made by one block of switches. The generator provides obtaining rectangular voltage pulses of up to 130 -140 kV with the duration of 10 μs at the matched load and 5 μs at an arbitrary constant resistive load, respectively. Assembling the stages from two half-length parallel lines, results in possibility to increase the output voltage and current of the generator.
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The possibility of using method for measuring the absorbed energy by means of a shunt current was considered. Experimental results of such measurements in a plasma of pulsed electric discharges excited by nanosecond voltage pulses, which are applied to a nonlinear load through long transmission line, are presented. A comparison was made with the technique of measuring the absorbed energy by means of a voltage divider and a shunt current located directly in the load.
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In this paper, in addition to the well-known ambipolar diffusion, ambipolar drift and plasma transport based on the action of the electric field energy are considered. The importance of the mechanisms of ambipolar plasma transport at the formation of a discharge structure in gases of medium and atmospheric pressures using experimental works as an example is demonstrated.
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The paper reports on a study of a supershort avalanche electron beam (SAEB) formed in atmospheric pressure air in a diode with dielectric films. The study shows that the number of electrons downstream of an Al foil anode increases gradually as a dielectric film 50 μm thick is shifted from cathode to anode. With a film 100 μm thick placed at 3 mm from the cathode, the number of electrons decreases ∼4 times, whereas their number with the same foil placed at 1 and 11 mm decreases by no more than 30 %. It is supposed that the dielectric at 3 mm from the cathode substantially influences the formation of an ionization wave and that increasing its thickness causes a rapid decrease in SAEB amplitude.
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The kernel construction for the biomedical data classification using Support Vector Machine based on Green function for Ornstein-Uhlenbeck equation is presented. Quantitative estimates of classification quality of exhaled air samples absorption spectra for patients with chronic obstructive pulmonary disease and healthy volunteers were carried out.
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The study of exosomes of saliva and blood plasma by THz laser spectroscopy was carried out. Exosomes were sampled from patients with colorectal cancer (n = 6) and healthy volunteers (n = 5). A substantive examination of the samples absorption spectra was performed using the method of canonical correlation analysis. The presence of Glycine, LAlanine, Mannose was revealed everywhere. The Mannose content was less in exosomes samples corresponding to colorectal cancer in comparison with exosomes samples from healthy volunteers.
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The paper presents the results of study some dynamic characteristics of the copper brightness amplifier. The active medium of the copper vapor laser was used as a brightness amplifier. The time dependence of the gain is considered. Optimal time delays between the reflected signal and the amplified are presented. The results of the study can be used for the developing of visualization systems by means of such image brightness amplifiers.
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The paper presents experimental results of the investigation of microstructure of copper surface layer after treatment by runaway preionized diffuse discharge in a stream of atmospheric nitrogen. It is shown that after 100,000 processing pulses on the surface of copper specimens, a disoriented surface layer with a depth of up to 200 nm is formed. Moreover, the results of X-ray phase analysis did not reveal changes in the phase composition of the surface. However, as a result of surface treatment by plasma of a diffuse discharge, the lattice becomes larger and the microstress increases.
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The influence of Н2О2 on the degradation of 8-methoxypsoralen (8-MOP) in water-ethanol solutions under the action of KrCl and XeBr excilamp radiation in a photoreactor is investigated. A kinematic model of photodegradation of the investigated molecule is constructed. In water-ethanol solutions the addition of Н2О2 altered the mechanism of decay of 8-MOP under the action of a KrCl excilamp in comparison with irradiation by a XeBr excilamp. This behavior is explained by the fact that the action of 283 nm radiation leads to accumulation of a stable photoproduct. In order to establish the toxicity of this product further research is needed.
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Recently synthesized pyrrolanthrone, naphtho[1,2,3-cd]indole-6(2H)-one (PyAn), and its water-soluble derivative, 3(naphtho[1,2,3-cd]indole-6(2H)-one-2-yl) sodium propylsulfonate, are very promising for anticancer therapy due to both the fluorescent and cytotoxic properties. The present study is focused on the spectroscopic analysis of solvent effects in PyAn and its derivative. An increase of the solvent polarity results in the bathochromic shift in emission and absorption spectra that indicates the involvement of ππ*-type transition. The double linear correlation of Stokes shift with bulk solvent polarity functions (in terms of Lippert’s, Bakhshiev’s and Chamma-Viallet’s models) and microscopic solvent polarity parameter ( ) 30 N ET for aprotic and protic solvents is observed. Both general and specific solvent effects are revealed for the solute-solvent systems. Fluorescence quantum yield, fluorescence lifetime and excited-state dipole moment were defined for PyAn and its derivative in different solvents for the first time. The obtained information is of a great importance for the characterization of intermolecular interactions of drugs with biomolecules for the development of new drug delivery systems.
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We report results on comparative study of SHG in powder of promising nonlinear γ-Ga2S3 crystal. Digallium trisulfide powders with particle size from 20 μm to 500 μm were tested in comparison with powders of well-known LBO, BBO, KABO, KDP, and LN crystals under the pumping by 7 ns 1064 Nd:YAG laser. Laser-induced damage threshold of different powder fractions were determined. The γ-Ga2S3 shown high damage threshold and large SHG intensity: 56 times to that in LBO powder, 15 in BBO, 50 in KABO, 67 in KDP, and 3 in LN (for particle size: 20–50 μm), that renders it amongst the most promising crystal for frequency conversion of high-intense nanosecond radiation of near-IR lasers by optical rectification technique.
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Ultrashort pulse (USP) fiber lasers have found applications in such various fields as frequency metrology and spectroscopy, telecommunication systems, etc. For the last decade, mode-locking (ML) fiber lasers have been under carefully investigations for scientific, medical and industrial applications. Also, USP fiber sources can be treated as an ideal platform to expand future applications due to the complex ML nonlinear dynamics with a presence of high value of group velocity dispersion (GVD) and the third order dispersion in the resonator. For more reliable and robust launching of passive mode-locking based on a nonlinear polarization evolution, we used a highly nonlinear germanosilicate fiber (with germanium oxides concentration in the core ~ 50 mol. %) inside the cavity and we have obtained ultrashort stretched pulses with a high peak power and energy. In this work relative intensity noise and frequency repetition stability is improved by applying isolator-polarizer (ISO-PM) with increased extinction ratio Pext and by compensation of intracavity group-velocity dispersion from the value β2 ~ - 0.021 ps2 to ~ - 0.0053 ps2 at 1550 nm. As a result, we have obtained the low-noise stretched pulse generation with duration ~ 180 fs at a repetition rate ~ 11.3 MHz (with signal-tonoise ratio at fundamental frequency ~ 59 dB) with Allan deviation of a pulse repetition frequency for 1 s interval ~ 5,7 * 10-9 and a relative intensity noise < -101 dBc / Hz.
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Results of theoretical research for two psoralen molecules: 8-methoxypsoralen and khellin are presented. Schemes of photophysical processes in psoralens based on quantum chemical calculation by the INDO method are analyzed. The rate constants of intersystem and internal conversions are calculated. We obtained rather high intersystem conversion constant that influences on the fluorescent yield of 8-methoxypsoralen (107 s-1) and an insignificant constant of intersystem conversion for khellin (103 s-1).
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The control system for bistatic laser monitor was developed. This system includes digital circuit and high-voltage modulator. The control system provides synchronous pumping of two active elements: an illumination source and a brightness amplifier. The time shift between triggering pulses is regulated by a variometer and its maximum value is 40 ns in case active load. The MOPA system was realized. Experiments on visualization of a test object were done. The example of such visualization was demonstrated.
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One way to obtain a multi-terawatt laser beams in the visible spectrum rang is direct amplification of the pulse in the output amplifier. Such method is being developed in IHCE SB RAS based on THL-100 hybrid laser system. This system uses solid-state and gas active media, namely: Ti:Sa femtosecond front-end and photodissociative XeF(C-A) amplifier. The front-end generates a transform-limited radiation pulse of 50 fs duration or a positive-chirped 50 ps pulse (FWHM) on second harmonic (475 nm). The XeF(C-A) amplifier can amplify the energy of front-end pulse up to 2-3 J. A compressor is required to recompress the amplified 50 ps radiation pulse to the transform-limited pulse duration. In this paper, we present the calculated parameters of the compressor based on the diffraction gratings and experimental data of the output radiation pulse compression of the front-end. The compressor optics scheme, its parameters and adjustment technique are presented. The compressing possibility of 50 ps second harmonic pulse to a duration of 75 fs in the grating compressor at a pulse energy of 7 mJ and a 1 cm beam diameter are demonstrated.
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A series of laboratory and full-scale experiments on the propagation of high-power terawatt radiation on the basis of a femtosecond stand of the IAO SB RAS have been carried out. The problem of the spreading of femtosecond pulses in air is considered. The results of the investigation of dispersion spreading of pulses of femtosecond duration are presented.
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Spectral, photophysical, photochemical characteristics for mononuclear and binuclear dipyrromethenes in complexes with BF2 (BODIPY), bis-BODIPY and bis-helicates ([Zn2(L)2]) are described. The role of substituents (type and location in the ligand) and the medium in which dipyrromethene complexes are placed (solvents, solid-state matrices), the effect of different complexing agents (p- and d-elements) on the photonics of the complexes are discussed. The results of studying the lasing and photochemical properties of complexes under the action of laser irradiation are presented. In addition, for the described complexes the stability in the ground and excited states in protic media are estimated. Based on the analysis of the results discussed possibilities of practical application of these compounds to creating various optical devices.
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Soil fungi are actively involved in the processes of humic substances synthesis, transformation and mineralization due to production of extracellular nonspecific oxidative enzymes. The work was aimed to evaluate using spectral methods transformation dynamics for the humic product (HP) from lignosulfonate (HPligno) by filamentous soil fungal cultures Alternaria alternata and Trichoderma harzianum. Experiments showed that direct spectroscopic study of HPligno introduced into the nutrient medium and its transformation during fungal growth is challenging due to strong absorption of light by nutrient medium, development of absorbing fungal metabolites, partial utilization and destruction of HP by fungi and therefore due to the need to register tiny changes in overlapping bands. To accomplish that task we proposed a novel algorithm for processing the absorption spectra, which has not previously been used to study fungal cultures. We calculated the second-order derivative in respect to wavelength for absorption spectra measured during fungal growth and found characteristic "patterns" for introduced HP: a maximum at 270-285 and a minimum within 290-300 nm. The spectral index determined from amplitudes in the second-order derivative spectrum reflects the relative content of HP in the nutrient medium in presence of other absorbing components. We resume that two fungal strains utilized HPligno in the 0,02 and 0,1% concentrations better at 30 g/L sucrose than at 3 g/L in the medium. Thus the second-order differentiated absorption spectra helped to quantify degradation of the HPligno during fungal growth.
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The work shows that iron oxide nanoparticles obtained in acoustoplasma discharge with cavitation affect the rate of one of the reactions of the process of blood coagulation - cleavage of fibrinogen by thrombin. As a result of the reaction, a fibrin gel is formed. By means of dynamic and static light scattering we reveal that adding of thrombin initially mixed with nanoparticles to the fibrinogen solution leads to dramatically acceleration of gel formation. Adding of nanoparticles to the solution of fibrinogen (before thrombin addition) leads to stopping of the reaction at the first stage (without gel formation). This data shows that ferrous oxide nanoparticles can act as regulators of enzyme reaction - in one case accelerating it, and in the other - by inhibiting it. Previously we presented the dynamics of distributions of the scattered light intensity on particle sizes in the fibrinogen-thrombin system with various sequences of nanoparticle addition. In this work we showed dynamics of the intensity correlation function in the samples, whose form becomes close to “stretched exponent” in pregel state or power law in a gel.
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The paper presents the results of the experimental study of a copper bromide vapor active medium operation in the amplified spontaneous emission (ASE) mode with the pulse repetition frequency (PRF) up to 200 kHz. The oscillograms of the active medium radiation pulse at various frequencies in a generator (lasing) mode, single-pass amplification mode and ASE are presented. The possibility to use active media on self-terminating transitions as brightness amplifiers at PRFs higher than 100 kHz has been shown.
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The possibilities of realization of the output amplifier cascade of a powerful laser system based on parametric amplification of femtosecond pulses with multiple beams pumping are investigated. A method for choosing the optimal arrangement of the pump beams of a parametric amplifier which makes it possible to achieve a broad spectral gain band with minimal losses from parametric diffraction is proposed. A number of optimal arrangements of the pump beams in LBO and DKDP crystals are chosen. Simulation results of the parametric amplification taking parametric diffraction into account are presented for these crystals. The dependence of the amplification efficiency and the amplified pulse duration on the number of pump beams is analyzed. Complete elimination of modulation of the spatial profile of the amplified radiation is demonstrated with the use of spatial filters in case of LBO crystal. The influence of small-scale self-focusing of the interference pattern of the total pump beam on the peak intensity of beams is investigated for LBO and DKDP crystals. It is shown that DKDP crystals are of little avail for multiple pump parametric amplification of fs pulses in 700- 900 nm spectral range.
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