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The article addresses current issues in the field of fiber-optic data transmission, related to the constant increase in demand for communication system bandwidth and nonlinear response. The main machine learning methods used to compensate for nonlinear signal distortions in long-haul coherent communication lines are presented, including neural networks of various architectures. The paper emphasizes the promising nature of machine learning-based solutions to enhance the performance of optical fiber communication systems, thanks to their ability to derive effective and adaptive signal recovery schemes with low computational complexity.

Lasers of various power classes from tens of µW to tens of W based on the stimulated Raman scattering (SRS) effect in waveguide elements made of tellurite glasses are studied. Due to the high SRS gain and large SRS frequency shift, tellurite glasses are promising materials for the development of laser sources at a wavelength of about 2.3 μm with a pump at a wavelength of about 2 μm, which was used in the work. A detailed numerical simulation of Raman lasers based on single-core and multicore special tellurite fibers is carried out. It is shown that the conversion efficiency of pump power to SRS wave power for optimal parameters can exceed 50%. Detailed modeling of low-power Raman lasers based on high-Q microresonators is performed; optimal parameters and factors limiting generation are found.

Resonance properties of the local field of metal fractal clusters are considered. The effects of surface-enhanced Raman scattering, photoluminescence enhancement, and nonlinear responses are studied. It is demonstrated that the model developed by S. G. Rautian, based on the quantum theory of nonlinearity, offers a more accurate description than previous theories. Among the scientific results of the theory proposed by Rautian and his team, the following points can be highlighted: metal nanoparticles with a diameter < 30 nm exhibit discrete energy levels, in contrast to semiconductor quantum dots; Rautian’s theory provides an accurate description of the linear part of the dielectric function, corresponding to the classical Drude model; the cubic nonlinear susceptibility according to Rautian’s model is consistent with experiments, indicating the contribution of conduction electrons.

The article provides a brief overview of modern achievements in quantum information science, problems and prospects for the development of quantum computing. The elementary mathematical model of quantum computing and the concept of quantum supremacy are discussed. The use of ultracold atoms for the implementation of quantum processors is considered.

The problem of measuring the space-time and energy parameters of acoustic infrasound vibrations in the atmosphere based on the placement of laser and fiber lines in geoecological monitoring zones is considered. The measurements are based on the phenomenon of the acousto-optical transformation at infra-low frequencies associated with the influence of an external acoustic wave field on the characteristics of propagation of laser pulse beams in this field. Background and anthropogenic atmospheric acoustic processes are used as external sources of the field. The measured parameter is the phase (frequency) fluctuation atmospheric optical signal relative to the reference optical fiber signal. The characteristics of the atmospheric fiber laser system and some results of experiments aimed at estimating the statistics of phase fluctuations of atmospheric laser pulses and the parameters of infrasound fields in a given atmospheric monitoring zone are presented.

Solid and porous films of the Si _1-xGe_x alloys with a germanium content of about 40% and a thickness of 3-4 μm, formed on single-crystal silicon by electrochemical deposition of germanium into a porous silicon matrix followed by rapid thermal annealing at a temperature of 950 °C, are studied by Raman spectroscopy, optical spectroscopy, and scanning electron microscopy. Based on the Raman spectra taken in the Stokes and anti-Stokes frequency regions, using Boltzmann statistics and the Fourier thermal conductivity law, the thermal conductivity of the films is determined, which is found to be 7-9 and 3-6 W/(m×K) for a continuous and porous film, respectively. The low thermal conductivity of the porous film is explained by additional phonon scattering from the developed pore surface. The prospect of using such films in thermoelectric converters is ensured by the simplicity and scalability of the method for manufacturing the alloy, as well as its low thermal conductivity.

The method of Raman scattering (RS) is used to study samples of fossil coals from various deposits. An unusual form of the Raman spectrum of coal graphite from the Seregen deposit (Taimyr) is discovered. The spectrum consists of intense narrow bands, which are usually typical for single crystals, in contrast to the standard spectra for fossil coals, i.e., broadened D and G bands and a weakly pronounced second-order Raman spectrum. The studies have shown that there is no direct analogy between the spectra of the Taimyr sample of coal graphite and the Raman spectra of other allotropic forms of carbon. Based on the experiments carried out, it is suggested that there is a possibility of the existence of a new allotropic form of carbon.

The results of changing the parameters of pseudo-MOS-transistors on silicon-on-sapphire mesastructures under irradiation with swift heavy ions (SHI) Xe⁺²⁶ (150 MeV) and Bi⁺⁵¹ (670 MeV) to a fluence of 2´10¹¹cm^-2 are presented. They reveal the accumulation of mechanical stresses and charges in intermediate ferroelectric layers of HfO₂ (HO) films 20 nm thick and Hf_0.5Zr_0.5O₂ (HZO) films, laminated with Al₂O₃ monolayer inserts (HA, HZA) or without them. SOS heterostructures are formed by direct splicing and hydrogen transfer of 500 nm silicon films on HA and HZA nanolayers pre-deposited by plasma-enhanced atomic layer deposition on sapphire. The electrical parameters are determined from the Y-MOSFET drain-gate characteristics ( I_ds - V_g ) with 100 nm thick drain-stock W electrodes deposited by magnetron sputtering on the SOS mesastructures through a lithographic mask. A comparison of these characteristics with Raman scattering data shows that the mechanical compression stresses introduced by BTI irradiation in silicon correspond to the volume ratios of Xe and Bi tracks in HA ferroelectric and sapphire.

In this paper, we propose a technique for processing noisy spectral data, which allows implementing a mathematically sound selection of sharp signal peaks above an unknown smooth background, for which there is no reliable theoretical model. The main idea of the method is to construct an optimizing functional that predicts the most probable parameters of spectral lines. Unlike the Tikhonov regularization method, in which a smooth unknown function is extracted from the noisy signal, here we consider the problem of regularization of the superposition of a smooth background function with sharp peaks. The proposed approach provides an algorithm for processing experimental data that allows us to filter out random noise and determine both the parameters of the peaks and the background function with good accuracy. Finding the optimal regularization parameters is based on a priori assumptions about the smoothness of the background function and statistical properties of the random noise.

Based on the analysis of the main modern trends in the field of hyperspectral equipment construction, it is shown that the use of integrated optoelectronic circuits and optical nodes in planar design is promising when creating small-sized devices of a new generation focused on applications in ground-based surveillance systems. In particular, the expediency of using micro-mirror matrices in scanning systems and planar Mach-Zehnder interferometers in spectral separation systems is noted. This makes it possible to abandon bulky, slow, and not always reliable mechanical components and create devices with rapid registration of hyperspectral images.