Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 8

A new method for wireless byte-by-byte optical transmission of a digital signal multiplexed by the value of orbital angular momentum (OAM) of electromagnetic wave is presented. The transmitter is a round array of coherent laser beams formed by splitting original narrow-band laser radiation into eight channels. Data transmission channels with different OAM values are formed through interference combining of eight coherent laser beams in the far diffraction zone. The amplitude and phase of these beams vary proportionally to the values of Fourier images of information signals coming from the programmable controller to the amplitude and phase modulators of the round array of laser beams. The wave field propagates in space and comes at the input of the receiving telescope. To demultiplex the signal, the sorter of OAM modes is used. It comprises beam splitters, vortex phase plates, focusing lenses, photodetectors, and a comparator. The sorter distributes the incoming radiation into eight channels, which differ in the OAM values in the range from -3 to +4. Upon the processing, the structure of a digital signal byte is reconstructed at the vortex phase plates at the photodetectors inputs. The combining of eight laser beams in the comparator yields the complete structure of the transmitted digital signal. A conceptual diagram of an experimental setup implementing this method is proposed. The possibility of its practical implementation is demonstrated through numerical simulation. Some technical methods improving the efficiency of the method are suggested, and the advantages of the method are described.

Dependence on time and conditions of propagation of a laser beam integral (radius and displacement of the energy center) and local (intensity at a point) parameters was determined numerically. The obtained functions were expanded into a trigonometric Fourier series, and the precision of expansion was assessed. The mathematical models are presented as software applications, using which the dependence of the frequency of spectral components on the wind speed and the inner turbulence scale were derived. The results of the study can be used in the design of adaptive optics systems, in particular, for formulation of requirements for frequency of correction for atmospheric distortions, which is one of the main characteristics of laser beam control unit.

Results of a laboratory experiment with a laser beam propagated in an artificially created turbulence are analyzed. Methods are described which transform a sequence of video frames with recorded intensity distribution into characteristics of laser radiation. As a result of the expansion of time-dependent functions into a trigonometric Fourier series, the frequency of parameter variations was determined and requirements for the operating speed of an adaptive system designed to compensate for distortions were formulated.

To detect ecotoxicants in the atmosphere by absorption spectroscopy, it is necessary to know their spectroscopic parameters. The absorption spectra of chloroform in a gas phase in the 2-mm wavelength subranges, where spectroscopic data are absent, were measured using high resolution spectrometer with phase-switching. The experimental results were compared with theoretical estimates of the absorption rotational line central frequencies. After preliminary measurements in the 118.6-118.9 GHz subrange, their comparison with the literature data, and confirmation of the possibility of reliable detection of absorption lines in the spectrum, the absorption lines for CH³⁵Cl₃ in the ground and in excited vibrational states (ν₃, 2ν₃) in the 131 ÷ 132, 137 ÷ 139, 150 ÷ 152, and 156 ÷ 158 GHz spectral ranges have been revealed and identified. Presented results can be used for detection of CH³⁵Cl₃ in the atmosphere.

The article analyzes the quality of collections of experimental vibrational-rotational energy levels and transitions of the main isotopologue of the water molecule placed in the information system (IS) W@DIS. Software for automatic support of the quality of the collection of energy levels and transitions when loading new data sources was created. This software performs sequential double filtering using the latest version of empirical energy levels, as well as quasi-empirical energy levels. A brief description of the introduced quasi-empirical energy levels and their role in updating the quality of data is given. Statistical data on each of the collections are presented, subsets of collections suitable for decomposition of expert wave numbers and lower-level energies are distinguished.

This study is devoted to the development of a trace method for monitoring tritium isotopologues of water (HTO and T₂O) using infrared (IR) spectroscopy. The actuality of the work is due to the need to monitor tritium, a radioactive isotope of hydrogen formed as a result of man-made processes, including accidents at nuclear power plants. The main objective was to estimate the sensitivity of IR spectroscopy for detecting low concentrations of HTO and T₂O in water vapors, which is critical for the operational monitoring of radioactive contamination. The work uses spectroscopic data from theoretical calculations and experimental measurements, including absorption line parameters from the spectra.iao.ru and HITRAN2020 databases. The line-by-line method is used to simulate transmission taking into account the refined line broadening coefficients calculated using the author's technique. The main results include: improved line broadening parameters, which increased the simulation accuracy; revealing of optimal spectral ranges for detecting HTO (1227-1236, 2219-2226 cm^-1), and the intervals for T₂O (930-990, 1092-1010 cm^-1) located in the atmospheric window (8-12 μm); estimation of the detection threshold for tritium isotopologues at a level of 0.01-0.05% of the concentration of the main isotopologue H₂¹⁶O. The obtained results open up opportunities for creating real-time tritium monitoring systems, which is important in assessing environmental and radiation risks. Promising areas for further research are adaptation of the method to field conditions taking into account the atmospheric influence and integration of spectroscopic data into climate models. The work contributes to the development of environmental monitoring and radiation safety methods.

When studying the propagation of optical radiation through the atmosphere, it is important to take into account its possible distortions due to turbulence of temperature and wind fields. The dependence of the structure characteristic of the refractive index of optical waves in the surface air layer on temperature gradients and wind velocity, as well as on turbulent heat fluxes and friction (dynamic) velocity is considered based on experimental data received in 2024 at the Basic Experimental Observatory of Institute of Atmospheric Optics SB RAS (Tomsk, Russia) with an ultrasonic anemometer-thermometer (ultrasonic weather station) and a meteorological temperature profiler. Some regularities are identified in the correlation between the structure characteristic and the meteorological parameters. It is noted that high values of the structure characteristic can take place under conditions of temperature inversions. The results can be useful in solving problems of atmospheric optics, in particular, propagation of laser radiation.

Use of high stacks for removal of hydrocarbon fuel combustion products at thermal power plants allows to significantly reduce air pollution levels. The article discusses a method for estimating the rise rates and buoyancy flows of smoke emissions from thermal power plant stacks based on similarity and dimensionality relationships, hydrodynamic models, and satellite information. The proposed method was tested using a winter satellite image of smoke plumes and their shadows on the earth's surface as applied to the high stacks of the Gusinoozerskaya GRES. The wind and air temperature fields were calculated using the WRF mesoscale model adapted to the Baikal natural territory. The results of the study enable, under conditions of very limited input information, to characterize the active stage of smoke plume rise and to monitor the modes of impurity emissions from industrial enterprise stacks based on buoyancy flow estimates.

Snow cover is an effective accumulator of dust fallout and provides objective information on the level of pollution. Pollution is among key factors that determine life quality in a city and is seriously considered when it comes to people’s residence preferences, house building policy, migration, and other aspects of urban environment management. Accurate pollution estimation and town zoning by pollution level based on these estimates are, therefore, challenges to be taken up in big cities with highly developed industries. This paper deals with the results of the 2018 study of the distribution of snow cover dust loading across Krasnoyarsk. Based on the norm, dust loading appeared to vary from low to high among the city districts. In winter 2018, dust loading dropped averagely 1.3 times as compared to the previous study. The northern and eastern industrial zones (Soviet and Lenin Districts, respectively) encompassing large industries were under the highest dust pollution. The dust pollution of snow cover was low in Krasnoyarsk in 2018.

The paper presents a database of backscattered light matrices for all typical shapes of ice crystals in cirrus clouds, including an aggregate of eight hexagonal columns, which is often used in research. The case of random orientation of a particle in space is considered. A unique feature of this database, in contrast to its analogues, is that it presents solutions for all typical convex crystals of cirrus clouds, as well as particles of a typical non-convex shape - an aggregate. The solution is derived for the particle size range from 10 to 1000 mm for three most commonly used lidar wavelengths: 0.355, 0.532, and 1.064 μm. This database is extremely important for the development of algorithms for interpreting laser polarization sounding data from cirrus clouds using both ground-based and space-based lidars. The database is available in the public domain in a simple text format to facilitate its use by a wide range of scientists.

The paper discusses approaches to increasing the background immunity of the laser fragmentation/laser-induced fluorescence (LF/LIF) method in remote detection of surface traces of organophosphates. The possibility of inducing anti-Stokes fluorescence of PO-fragments (phosphorus oxide molecules) of organophosphates from the first excited vibrational state X ²Π ( v'' = 1) to the electronically excited state A ²Σ⁺ ( v' = 0) by laser radiation at wavelengths of 253.891, 254.021, 255.337, and 255.484 nm near the bandheads of the branches ( Q ₁₁ + P ₂₁), P ₁₁, ( P ₂₂ + Q ₁₂), and P ₁₂, respectively, was experimentally shown. Using the example of drop-liquid traces of triethyl phosphate on a paper surface, it was determined that excitation of P ₁₂ branch lines forming the bandhead ensures the highest background immunity of the LF/LIF method for detecting organophosphates. The results can be used to select the optimal method for excitation of fluorescence of PO-fragments in the practical implementation of the LF/LIF method for remote detection of organophosphate traces.