This PDF file contains the front matter associated with SPIE Proceedings Volume 12920, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Visible Raman spectroscopy provides useful information about hydrocarbon fluid inclusions in crude oils. In particular, the presence or absence of hydrocarbon functional groups may be qualitatively determined. It is known, there are 12 Oil-Gas Production Companies in Azerbaijan, including 8 owned by Azerbaijan and 4 Joint Companies. In most oil spills situations, it is desirable to have more than one analytical technique for detecting of spilled oil to its suspected source. In this paper we present first results of Raman scattering spectra of crude oils excited by λ = 1064 nm laser line of YAG : Nd³⁺ laser line and taken from all Oil-Gas production Companies (in total twelve) of Azerbaijan Republic.

The results of the synthesis and study of the spectral and structural properties of borate glasses with (Cs,Rb)PbBr₃ perovskite nanocrystals are presented. (Cs,Rb)PbBr₃ nanocrystals exhibit intense narrow-band luminescence in the 510–520 nm region. With an increase in the rubidium content, the luminescence maximum of the crystals shifts to the short-wavelength region, while the luminescence quantum yield first increases to 91% and then decreases to 52%. In the rubidium absence, several perovskite-like phases of lead-cesium bromides are nucleated in the glass matrix: CsPb₂Br₅, Cs₄PbBr₆, and CsPbBr₃, while with the increase of the rubidium the CsPbBr₃ phase predominates. The glass matrix protects the (Cs,Rb)PbBr₃ nanocrystals from the ambient atmosphere, which leads to the stability of their luminescence intensity.

Numerical simulation of high-power femtosecond laser pulse propagation in air under conditions of amplitude modulation by metal wire-mesh masks are carried out. The use of such modulation masks leads to splitting of initial laser beam into separate parts (subbeams) of lower energy. Such spatial structuring of optical radiation causes large-scale diffraction interaction between subbeams, which leads to regularization of the diffraction pattern formed at the stage of pulse self-focusing. It is shown that the use of modulation meshes generally reduces the total length of the beam filamentation, but significantly increases the longitudinal continuity of the laser plasma density distribution in laser filaments. For full-scale meshes providing modulation of the entire beam area the formed filamentation region demonstrates larger extent than by using meshes with partial beam covering.

This work is devoted to the study of the generation regime of an ultrashort pulse bunch in an erbium-doped fiber laser with hybrid mode-locking in the region of a low positive total intra-cavity group velocity dispersion. The pulse bunch has an optical spectrum 33 nm wide with a central wavelength of 1530 nm and has 2 pulses inside with a duration of ~143 fs at the full-width-half-maximum. The radio frequency spectrum in the region of the main pulse repetition rate, equal to ~8.5 MHz, demonstrates, depending on the pump power, the presence of 4 to 8 side peaks associated with the second pulse in the bunch. A comparison of the single-pulse and multi-pulse regimes demonstrates a twofold increase in the average output optical power of a pulse bunch for equal pump power and cavity parameters.

All-inorganic mixed-halide perovskites are promising materials for a number of photonic and optoelectronic applications. Decent progress has been made in the field of the synthesis of their high-quality nano- and microcrystals exhibiting bright excitonic photoluminescence and laser generation tunable in a wide spectral range. However, the engineering of high-performance optoelectronic devices demonstrating long-term operational stability is challenging because of non-balanced charge carrier injection, Joule heating, and corrosion of metal electrodes. To balance charge carrier injection sandwich structures containing various electron- and hole-transport layers have been reported. To tackle the rest two issues utilization of a high thermal conductivity sapphire substrate as well as carbon electrodes could be the best choice. Herein, we employ 1030 nm fs laser source for the ablation of mixed-halide CsPb(Cl,Br)₃ microwires grown on sapphire and covered with a single-walled carbon nanotube (SWCNT) thin film to produce planar microstructures of SWCNT/perovskite/SWCNT type. It is established, for CsPb(Cl_xBr_1−x)₃, the damage threshold value increases linearly with chlorine content in the crystal lattice and goes beyond one for cut SWCNT thin film (F₀ = 0.68 J cm⁻²) when x ≥ 0.4. Thus, simple microdevices with tunable electroluminescence and spectral responsivity can be produced. We believe our findings will speed up progress in the development of a new platform for planar optoelectronics.

Semiconductor nanowire (NW) lasers is a promising field of research in many scientific groups around the globe. Their main advantages over nanocuboid and microdisk lasers are two naturally formed light outputs and the shape affording the precise pick-and-place integration of the outputs with light couplers to deliver it on a microscale in photonic integrated circuits (PICs). Although there is good progress in epitaxially grown A^IIIB^V and A^IIB^{V I} NW lasers, cost-efficient counterparts are in demand to supersede the former on the market. For this, a decent option could be non-epitaxial all-inorganic halide perovskite NWs demonstrating a low concentration of deep charge carrier trap states and high enough optical gain and refractive index to enable low-threshold high-Q laser generation in a Fabry−Pérot cavity at room temperature. However, optical pumping of NWs by continuous wave or pulsed excitation at a high repetition frequency is, most likely, supposed to occur in photonic devices that might result in deterioration of NWs photoluminescence, in particular lasing. Herein, we report on the temporal stability of laser and spontaneous emission in a series of mixed-halide CsPb(Cl,Br)₃ perovskite NWs grown on a sapphire substrate by sublimation method. We identify a threshold fluence for isolated NWs upon fs pulsed UV-laser excitation at low repetition frequency and, then, examine them at 100 kHz. It is established that an increase in Cl content in the crystal lattice not only shortens a period of lasing observation but also results in halide segregation phenomena.

This paper presents the results of modeling the antireflection surfaces on a diamond by creating a periodic structure (alternating channels) on its surface. The results of modeling using various forms of channel sections and geometric parameters are considered. Calculated transmittance spectra for all the presented structures are obtained. The dependencies between the geometric parameters used and the received transmittance spectra are established.

The spectral line profiles of helium atoms in laser fields are simulated within the framework of the method based on the numerical solution of the non-stationary Schrödinger equation. The proposed method is free from limitations of perturbation theory and makes it possible to calculate the emission spectra of atoms both under non-resonant and resonant excitation by the electric field. The algorithm of this method is implemented in the StarkD software package written in FORTRAN and Maple. Within the framework of the proposed method, the behavior of the helium spectral line profiles is studied under changing electric field frequency in the range of 10⁵ – 10⁷ MHz, which is typical of lasers. A comparative analysis of the behavior of the helium spectral line profiles in resonances and interresonance regions is carried out. Practical applications of the obtained theoretical results are proposed.

Laser and discharge parameters in mixtures of rare gases with halogens driven by a pre-pulse-sustainer circuit technique are studied experimentally and theoretically. Inductive energy storage with semiconductor opening switch was used for the high-voltage pre-pulse formation. It was shown that the pre-pulse with a high amplitude and short rise-time along with sharp increase of discharge current and uniform preionization allow to form long-lived stable volume discharge in halogen containing gas mixtures. UV laser pulses with total duration up to 450 ns were easily obtained. Another way for development of a long-lived diffuse plasma was suggested. Diffuse discharge was formed in a sharply inhomogeneous electric field by run-away electrons when using high voltage pulses of ns duration Efficient VUV lasing was obtained at wavelengths from 148 to 193 nm on the transitions of hydrogen, fluorine and exciplex ArF* molecules in mixtures of rare gases with additions of hydrogen and fluorine at pressures up to 10 atm.

It has been demonstrated how a longitudinal capacitive discharge can effectively pump pure metal vapor lasers. Prior to this, a similar type of discharge was used to pump of low-temperature self-terminated metal halide vapor media. In our work we used copper as the working metal. Two small volume active elements, which were 8.3 and 20 cm³, were made. For the first GDT (volume 8.3 cm³), a power of 1.5 W was achieved at an excitation pulse repetition rate of 55 kHz; for the second GDT (volume 20 cm³), a power of 2.6 W was achieved at a frequency of 35 kHz. For the first time, it has been experimentally shown that such a GDT design is suitable for obtaining high-frequency generation of pure metal vapor lasers.

Photoluminescence spectra of various samples made of polymethyl methacrylate (PMMA) induced by 222-nm-wavelength radiation of a KrCl excilamp with a bandwidth of ~ 2 nm and a narrow-band KrCl laser, as well as transmission spectra of these samples, have been investigated. It was found that the PMMA samples, according to their transmission spectra, can be divided into three characteristic groups with different short-wavelength transmission edges, which affect the photoluminescence spectra. It has been shown that the photoluminescence spectra of PMMA samples in the ultraviolet and visible regions depend on the power density of the exciting radiation.

The development of nanosecond discharge in 2-mm point-to-plane or point-to-point gaps filled with distilled water has been studied with a fast-framing device. Positive nanosecond voltage pulses with an amplitude of 25 kV (50 kV in idle mode) were applied via a 75-Ohm transmission line to the gap. The pointed electrodes were made of pieces of sewing needles. Time-resolved images of discharge were taken with a four-channel intensified charge-coupled device (ICCD) camera with simultaneous recording voltage and current waveforms with an 8-GHz oscilloscope. The ICCD camera takes three consecutive and one time-integrated image. It was observed that one or several streamers appeared on the surface of the positive needle tip. They branched forming a semblance of a crown that occupied a large region near the needle. When reflected pulses with negative polarity arrived on the pointed electrode, streamers did not grow. When the next positive pulse arrived on the pointed electrode, the streamers began to grow again, while actively branching. In the point-to-point gap, streamers developed from both needles. The collision of streamers was observed. A bright light flash accompanies the collision. A long afterglow was observed in the place of streamer collision.

The plasma of the filamentation region of femtosecond radiation is an intra-atmospheric source of radiation that can be used in the problem of remote sensing. The glow of the plasma of the filamentation region in the atmosphere is due to the emission at the transitions of the first negative (B₂Σ_u⁺→X₂Σ_g⁺) and the second positive system (C₃П_u→B₃П_g) of molecular nitrogen. By varying the energy and duration of the femtosecond radiation, it is possible to change the luminescence intensity of molecular nitrogen at the indicated transitions The report presents the results of a study of a relation of an initial energy and pulse duration with an intensity of a molecular nitrogen. It is shown that for certain values of the pulse duration, the change in the intensity of the luminescence of molecular nitrogen at wavelengths of 315.9, 337.1, and 357.7 nm of the second positive nitrogen system weakly depends on the initial energy.

The intensity saturation during self-focusing of high-power ultrashort laser radiation in an optical medium is considered. The propagation of a femtosecond laser pulse in air from the collapse stop point to a nonlinear focus are considered in detail. The criterion for stopping the intensity collapse is established in the approximation of the nonlinear Schrödinger equation. This criterion makes it possible to take into account the nonlinear activity of various optical media during the propagation of high-power femtosecond laser pulses. The parameters of the effective permittivity model that satisfy this criterion are determined.

Based on electro-optical measurements in the THz region and comparison with data from other authors, estimates of the nonlinear optical coefficient of GaSe crystals with varied degrees of sulfur doping are provided. The d22 value for GaSe was 13.9 pm/V at a laser wavelength of 1.55 microns. The acquired data are compared with the values of nonlinear coefficients for undoped GaSe samples provided in the works of other authors. The qualitative correspondence of experimental measurements of the nonlinearity coefficient and the empirical model based on Miller's rule in the range of 0.63 – 1.55 microns is shown. The inaccuracy of theoretical curve in comparison to the experimental one is around 10%. The techniques described in the paper for calculating the nonlinear optical coefficient's magnitude and the results obtained will make it possible to establish the foundation for the creation of radiophotonics devices based on unalloyed and sulfur-doped GaSe crystals.

The history of classical optics is associated with dielectric lenses, with a Mie size parameter, q=2πR/λ (where R is the radius sphere, and λ is the radiation wavelength) of about q>100, where the geometrical optics approximation is valid. The optically resonant dielectric nanostructures with a high refractive index has the size parameter of the one, q~1. But the dielectric particles with q ~ 10, are in the region between the wave and geometric optics turned out to be a "black spot" on the map of dielectric photonics. However, the studies on the optics of dielectric spheres of mesoscale sizes over the past twenty years, discover a number of unusual phenomena, including optical vortices, single and double both photonic nanojets and photonic hook, high-order Fano resonances, and the excitation of giant magnetic fields. The report gives a brief overview of these phenomena. The presence of a number of interesting applications indicates a new promising direction in photonics called mesotronics.

Tunable photonics is a booming field, allow to revolutionizing basic research of mesotronics. Recently we demonstrate innovative proof-of-concept of the time domain self-bending photonic hook (TD–PH) structured beams. Such near-field nonevanescent beam was generate by natural phase-change material as a mesoscale freezing water microdroplet. Such TD-PHs open applications in many fields, including microscopy, sensors, optical switching, temporal optics, optomechanical tweezers, materials processing, biomedicine, and so on. Moreover, new ways to generate photonic hooks have recently been proposed, such as: dual dielectric structure, double photonic hooks under both continuum wave and pulsed illumination. A new quality-criterion of the photonic hook beams was proposed.

The microstructure and tribological characteristics of the surface of structural steels E3310 and A290C1M and chrome vanadium cast iron after laser treatment (LT) are studied. For steel E3310 after LT (P=100 W) the structure of lath martensite and upper bainite is formed. For A290C1M steel (P=100 W, V=2 mm/s) the upper layer in the hardening zone is remelted, has the highest microhardness and martensite structure, below there is a martensitic-bainitic microstructure. The maximum depth of hardening at E3310 steel is 310 microns, for A290C1M steel is 170 microns. Microhardness for steels increases by more than 2.0 times. At the LT of cast iron with a slight melting of the surface, this increase is more than 4.0 times. In the melting zone the main structure is martensite, and in the quenching zone the ledeburite structure prevails. The hardening depth is 220-310 microns; the maximum microhardness value is 820 HV_0.1. No significant changes in the structure of cast iron were detected at the LT without melting. As a result of sliding friction tests, it was found that the decrease in linear wear and the wear intensity after LT is 26.6% and 43.9% for steels E3310 and A290C1M, respectively. For cast iron, the wear intensity after LT with melting is reduced by more than 100 times, linear wear – by more than 50 times, and the coefficient of friction – by almost 30 %.

Seven possible variants of the sodium atom excitation are considered for creating a polychromatic laser guide star (LGS). It has been shown that the 4²P_3/2 ← 3²S_1/2 transition excited at a wavelength of 330.237 nm is most suitable for creating a polychromatic LGS in sodium vapor using the effect of cascade fluorescence at one-photon excitation. In this case, the excitation efficiency will be 2 orders of magnitude lower compared to the efficiency of creating a monochromatic LGS at a wavelength of 589 nm.

In this paper we examined an ensemble of 50 large ice crystals of irregular shapes. To optimize calculations, each particle has no more than 20 faces that were randomly generated. The calculations were performed for particles with a size of 15 microns, with an incident radiation length of 0.532 microns. It is shown that for an ensemble of particles a coherent peak appears in the vicinity of the backward scattering direction, as well as the effect of negative polarization, which we studied in detail on a fixed shape of a single particle.

The use of modern nonlinear optical crystals (silver thiogalate (AgGaS2), etc.) as active media of optical resonators made it possible to develop and create a highly monochromatic (radiation width less than 1 cm-1) pulsed parametric laser with a wide tuning of the radiation wavelength (from 400 nm to 9100 nm). This paper reports on the operational (during one light pulse with a duration of 20 ns), local (laser spot diameter varies from 50 μm to 10 mm) and high-precision (error no more than 10%) determination of the composition, structure of molecules and their concentration of medicinal substances (drugs). The relevance of this problem is due to two reasons: the identification of counterfeit or poorly produced drugs and the demonstration of the possibility of a parametric laser in the fundamental study of the physicochemical properties of complex organic molecules, the natural vibration frequencies of which fall within the range of tuning the wavelength of pulsed radiation. parametric laser. In this work, a computer simulation of the process of resonant interaction of the radiation frequency of a tunable laser with the natural vibration frequencies of drug molecules was carried out. Using the described OPO, it is possible to register vibrational-rotational spectra, followed by mathematical processing and determination of the main physico-chemical parameters of the studied drug, by the method of differential absorption and scattering.

For studies of algorithms for stabilizing laser radiation during propagation in a randomly inhomogeneous medium, the problem of emulating atmospheric turbulence with the condition of repeatability of atmospheric parameters becomes topical. The second problem is to increase the speed and accuracy of the adaptive optical system by minimizing the error that occurs due to the displacement of the recorded beam image at the input aperture of the system during the time between frames caused by the turbulent atmosphere. A description is given of the stand of an adaptive optical system operating in the mode of emulating the tilts of the laser radiation wave front on a turbulent path with an additional loop for advanced correction of the beam tilt angle error due to the delay of the correcting Tip-Tilt mirror.

Based on the program for visualizing measurements on the photosensitive matrix of a video camera, the results of estimating the noise in measurements obtained using a tracking adaptive optical system are presented. Methods for improving the noise immunity of measurements on the stand of a tracking adaptive optical system are proposed.

Aiming at the problem of high laser power requirements in the long-distance application of LiDAR, combined with the advantages of long-distance detection capability of linear frequency modulation continuous wave, this paper proposes a pulse compression real-time processing technology based on LiDAR data module FPGA. Matlab software is used for parameter simulation, and then FPGA algorithm is used to implement the real-time frequency domain pulse compression processing. By comparing verilog simulation and Matlab simulation results, the feasibility of digital pulse compression real-time processing system design in this paper is verified.

An online and automated measurement approach based on LiDAR point cloud data for luggage dimensions is proposed, in order to enhance real-time precision and accuracy in luggage dimension measurements. This method is applicable to stationary luggage at airports and stations. Firstly, luggage point clouds are rapidly extracted based on scene information. Secondly, luggage types are determined based on luggage characteristics, which include regular and irregular luggage. Finally, luggage dimensions are computed to obtain the length, width, and height of the luggage. The experiment demonstrates that this method can achieve efficient measurement of luggage dimensions for various shapes, which presents certain practical value.

The work is devoted to the investigation of gain complex dependency on the pump radiation parameters. The dependencies of the pulse energy gain and the parameters of the amplified radiation on the parameters of the pump radiation in the amplifying cascade based on Yb:YAG active elements are experimentally studied. Small-signal gain with the magnitude of 19 was reached in three consecutive active elements with good beam quality and high pointing stability. A method is proposed for simultaneous experimental investigation of temperature and gain coefficient distributions. Thermal contribution to optical path difference is about 3 wavelengths of amplified radiation while the electronic contribution is 100 times smaller.

One of the main technical parameters of light emitting devices is their service life. The service life and stability of light radiation during operation determine the operating conditions of light sources. By the example of barrier discharge excilamps based on KrCl* (222 nm) and XeBr* (282 nm) exciplex molecules, an optoelectronic method for stabilizing excilamp UV radiation is proposed. The method consists in autocorrecting the radiation power of the excilamps using a UV radiation sensor and an electronic feedback that regulates the power of the excilamps. During of tests for the service life of KrCl and XeBr excilamps, the dependences of the change in the excilamp radiation power on time in a continuous mode of operation were obtained. A new approach to describing the reliability of excilamp operation is discussed. It is shown that instead of such a parameter of light-emitting devices as a useful service life, it is necessary to use a new quantitative characteristic, which is proposed to be called the guaranteed service life of the stable operation of the excilamp.

In the period from 2010 to 2021, in the village of Boyarsky on the eastern coast of Baikal Lake, studies were carried out on the vertical structure of aerosol fields in the troposphere. The measurements were carried out using the LOSA-M2 aerosol-Raman lidar in the summer (July - August). A total of 93 cycles of daily observations were carried out during this period. The report presents typical patterns of transformation of aerosol layers under various synoptic conditions. Particular attention is paid in the report to the relationship between the structure of the boundary layer and the direction of movement of air masses. With a southeasterly wind prevailing at the observation site and directed along the coast, a characteristic diurnal dynamics of the boundary layer is observed with the development of a mixing layer during daytime heating of the surface. When air masses formed above the cold surface of the lake are brought in, a layered structure without pronounced updrafts prevails.

This work presents the model calculations of the radiation attenuation of the lidars used to diagnose gas-aerosol pollution in the atmosphere in the range from UV to mid-IR. The contributions of the main atmospheric gases (vapor of H₂O, CO₂, O₃) as well as a number of industrial gases for the spectral ranges of the most prominent gas-aerosol impurities in the atmosphere for remote sensing using NIR and LWIR-lidars, are taken into account.

Lidar, as an important tool for studying atmospheric aerosol, is widely used in studying the distribution of atmospheric aerosol pollution. In environmental monitoring, especially when using mobile lidar for measurements, it's important to know not only situations of the pollution, but also the coordinates of their sources, and their dynamics distribution. The article introduces a method for calculating the coordinates of the objects locations according to the coordinates of the lidar, the detection direction and the distance between the lidar to the objects. Finally, the programming implementation of the method and its application in the development of auxiliary lidar systems.

Treatment of barley plants with “Epin-Extra” (active ingredient epibrassinolide) in field experiments, under conditions of prolonged drought, led to a decrease in the values of the fluorescent index (F_M−F_T)/F_T in the first weeks after treatment, indicating the decrease in the photosynthetic activity of the plants. In vegetative experiments with barley, under conditions of optimal soil moisture, on the contrary, a stimulating effect of this growth regulator on the photosynthetic apparatus of plants was observed. In laboratory experiments with the ornamental plants of tagetes subjected to 3-day exposure to low temperatures (about 5 °C), a decrease in the fluorescent indices Ф_PSII, NPQ, and F_M/F_T, recorded using PAM fluorometry, was observed. It is assumed that this result testifies to disturbances of the structural and functional organization of the photosynthetic apparatus of plants known from the literature. After preliminary, before exposure to low temperatures, treatment of plants with preparations "Epin-Extra" and silicon-containing liquid organic fertilizer "Siliplant" no such disturbances were observed.

Irradiation of microfungi Rhodotorula colostri by vacuum ultraviolet (VUV) radiation (λ=173 nm) in aquatic environment was studied. The results have shown, that the survival probability in the case of irradiation through a water layer (6 μ) increases up to 60% compared with the case without water layer. This increase can be explained by: 1) a decrease of intracellular water photolysis reactive products due to absorption of the short-wavelength part of the VUV spectrum by external water and 2) an insufficient of external water photolysis products to increase inactivation. This indicates a greater effectiveness of the impact on microorganisms of the reactive products of water decomposition from the inside than from the outside it. Since the short-wavelength wing is also absorbed when the water layer thickness is reduced to the minimum possible water layer thickness value d=1 μm, it can be recognized that the use of an external water layer for inactivation of spores by VUV radiation in the wavelength range λ=173 nm is ineffective.

The phenomenon of hormesis in different types of microsfungi, arising by the action of low doses of vacuum ultraviolet (VUV) radiation (λ=173 nm), was studied. An increase in survival probability (SP) have had all microfungi types: Cladosporium herbarum - SP= 215% at W= 0.23 mJ/cm², Pseudogymnoascus pannorum - SP= 130% at W= 0.13 mJ/cm² and Rhodotorula colostri - SP= 140% at W=0.005 mW/cm². The difference in irradiation doses at which the maximum of SP is recorded can be associated with the fact, that Cladosporium herbarum and Pseudogymnoascus pannorum are filamentous fungi, and Rhodotorula colostri has a yeast form. A smaller increase of SP value in Pseudogymnoascus pannorum and a shift in the position of the peaks to lower doses compared to Cladosporium herbarum, may be due to the fact that these types of spores have different pigmentation: carotene and melanin respectively. The observed survival probability increase may be due to growth of microscopic fungi number, that form colonies under the influence of VUV radiation.

In the work, the priority among a number of temperature mechanisms affecting the fluorescence ratiometric signal of fluorescein in the pH range of 5.5÷7 was revealed. The kinetic model at the monoanion-dianion dissociation step with temperature-dependent constants was applied to analyze the experimental data. It was shown that the major contribution to the sensitivity of the ratiometric signal on temperature provides the perturbation of the ionic equilibrium in the ground state. The thermometric characteristics of ratiometric signal were found and the temperature resolution of 7°C was achieved. Temperature resolution can be improved up to 2°C by optimization of the experimental conditions.

The effect of introducing of a halogen substituent into the structure of 2,2'-bipyridyl-6,6-dicarboxamide on the stability of their europium complexes has been studied. It is shown that, regardless of the size of the halogen atom, one complex particle is formed, and the metal-ligand stoichiometry of the complex is 1:1. The stability constants of europium complexes have been determined. A decrease in the size of the halogen atom leads to an increase in the stability of the complexes due to steric hindrance diminishing.

The influence of the introduction of chlorine atoms into the phenanthroline fragment of 2,9-phenanthrolinedicarboxamide on the stability constant of the europium complex has been studied. Only one complex particle is formed, and the stoichiometry of the metal-ligand complex is 1:1, regardless of the presence of acceptor substituent in the ligand structure. Presence of two chlorine substituents in the dicarboxamide leads to an increase in the stability constant of the europium complex by two orders of magnitude compared to the unsubstituted ligand.

The work is devoted to assessing the Fabry-Pérot effect in studying liquid and gas samples using THz spectroscopy. It has been shown that the right choice a measurement cuvette length, its window material and thicknesses can significantly decrease this effect. It allows more accurate identifying chemical composition of the sample.

The possibility of increasing the efficiency of Savitzky–Golay filter for THz absorption spectra noise reduction as a preprocessing step was considered. The studies were carried out on the model atmosphere gas mixtures typical for swampy area. The noisy absorption spectra of the gas mixtures in 0.1-1.0 THz spectral range were calculated using data from HITRAN database. A sliding window variant of Savitzky–Golay filter was proposed and analyzed. The analysis of noise reduction quality was evaluated by the criterion of proximity of two curves. Using Savitzky-Golay filter together with the sliding window method was shown to provide a significant improvement in the noise reduction compared to standard variant of this filter.

An approach to the study of the porous structure of metal-organic frameworks (MOF) using guest luminescent molecules with specially selected spectral characteristics as acceptors of electronic excitation energy was suggested. If such molecules are adsorbed in MOF pores with sizes comparable to the Förster radius, Förster resonance energy transfer (FRET) from photoexcited linkers occurs. In this case quenching of luminescence of the linker can serve as analytical signals indicating open pore structure of the MOF. The developed approach was demonstrated by the example of DUT-8(Zn) MOF and Coumarin 1 as guest molecules by time-resolved luminescence methods.

Dangerous high-power laser radiation has been used in technology for many decades, capable of damaging CCD and CMOS matrices (used in video cameras and lidars), as well as causing irreparable damage to the organs of vision. Damage occurs at a high-energy fluence density above a certain threshold value. The main disadvantages of the passive protection devices used – light filters – are color distortion and a narrow wavelength range that requires an accurate value of the wavelength of laser radiation that falls on a photosensitive material or device. The operation of a nonlinear optical limiter of laser radiation power for passive protection is based on the use of a material with a strong nonlinear optical response. However, existing materials do not have the low energy dimming threshold required for practice and, moreover, have insufficiently effective optical attenuation. Further improvement of these characteristics is necessary, although the results already achieved at the moment may well be used in practice. A nonlinear absorption coefficient was used to evaluate the effect of optical limiting. As a result of the studies carried out in this work on the example of composites of single walled carbon nanotubes with a tetra(cyclotriphosphazene)-substituted phthalocyanine ligand, we found that depending on the hydrodynamic radius of fine particles, the efficiency of optical limiting can increase by an order of magnitude. At the same time, the efficiency of optical limiting of composites is more than 2 times higher compared to the original nanotubes.

This article focuses on the top-seeded solution growth (TSSG) of single crystals of the low-temperature non-centrosymmetric modification of barium borate, β-BaB₂O₄ (β-BBO), using a mixed solvent comprising NaBaBO₃ and V₂O₅. We examine the linear absorption properties across a wide spectral range and nonlinear second harmonic generation (SHG) from 532 nm to 266 nm in β-BBO samples under Nd:YAG laser radiation pumping. The mean linear absorption for ordinary waves in vanadium-based crystals at wavelengths from 300 to 600 nm is found to be an order of magnitude higher than that in standard samples, measuring 0.0059 and 0.0007 cm^-1, respectively. However, crystals grown from the proposed vanadium-based solution still exhibit similar SHG efficiency to standard samples. Deviations from the quadratic dependence are observed at pump power densities exceeding 20 MW/cm², possibly attributed to temperature effects resulting from insufficient temperature stabilization.

The possibility of measuring pulsed X-ray spectra using a set of filter pairs including diffraction filters made of mosaic crystals of pyrolytic graphite (MCPG) and carbon attenuators with an equivalent value of the mass length is shown. The proposed spectral selection scheme is an alternative to broadband spectrometry with differential Ross filters used in the study of high-temperature plasma spectra generated by powerful laser or electric current pulses. The main advantages of the proposed spectrometric method are the possibility of continuous tuning of the spectral band width and the average spectrum energy. The use of carbon filters also allows the complete elimination of the balancing errors in absorption spectra that occur when using the Ross filters.

Spectral characteristics of luminescent emission of negatively charged nitrogen-vacancy (NV^–) centers in synthetic diamonds while filling of lower spin sublevels by microwave radiation were studied. On recorded spectra secondary side spin resonances induced by the hyperfine interaction between the NV^– center electronic spin and the ¹³C nuclear spin were found out on the frequencies of 2.8136 GHz and 2.9408 GHz.

The cathodoluminescence of two samples of synthetic diamond containing NV centers is investigated. Cathodoluminescence was excited by a high-current nanosecond electron beam. Cathodoluminescence spectra were measured in the temperature range of samples from 90 to 800 K. The obtained cathodoluminescence spectra were approximated and decomposed into Gaussian components.

The emission spectra of low-impurity diamond samples irradiated with electron beams of different densities were studied. Cherenkov radiation was obtained in all studied samples with an increase in the beam current density by more than 30%. The appearance of an excitonic band in the emission spectrum of one of the samples was detected with increasing beam current density.