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Background and Objectives: Magnetic fluids are unique nanodispersed systems that have the properties of a magnetic material and a liquid. Although their magnetic properties are inferior to steels and ferrites, they are supermagnetic compared to most liquid media. When a magnetic field is applied to a magnetic fluid, agglomerates of ferromagnetic nanoparticles are formed in it, which were visually observed in this work. Materials and Methods: The dependence of the modulation depth of laser radiation with wavelengths of 450 nm, 550 nm and 650 nm on the concentration of nanotubes and the magnitude of the magnetic field induction is studied. The transmittance of polarized radiation in the optical range is measured depending on the relative position of agglomerates of ferromagnetic nanoparticles and the vector of the electric field strength of laser radiation. The angle between the electrical component of the laser radiation and the magnetic field induction vector changes by rotating the laser diode and polarizer with a servomotor relative to the vertical axis. Results: The maximum value of the modulation depth for magnetic fluid without carbon nanotubes is 15% and is observed for laser radiation with a wavelength of 650 nm. Adding multi-walled carbon nanotubes to the magnetic fluid makes it possible to increase the modulation depth by approximately one and a halftimes. Conclusion: It has been revealed that with increasing wavelength of laser radiation, the modulation depth increases. As the magnetic field induction value increases, the modulation depth of polarized laser radiation increases for all wavelengths. The addition of carbon nanotubes to the magnetic fluid leads to their alignment along the agglomerates.

Background and Objectives: The activities of Professor Dmitriy Alexandrovich Usanov, Honored Scientist of the Russian Federation, Honored Inventor of the Russian Federation, at Saratov State University (SSU) were multifaceted, distinguished by high professionalism, a rare harmonious combination of scientific achievements and relevant applied solutions built on this basis. His achievements include organizational activities aimed at the development and support of research work at SSU at the world level, which was the most important trump card when Saratov University won the status of a National Research University, the development of the Department of Solid State Physics, which provides training of specialists in the direction of bachelor’s and master’s degree “Electronics and Nanoelectronics”, highly qualified personnel in the specialty “Miro electronic component base- and nanoelectronics, quantum devices”, support for the functioning of the network of dissertation councils at SSU and the publication of several series of journal “Izvestiya of Saratov University”, determining the policy and quality of publications in the journal “Izvestiya of Saratov University. Physics”, 30-year leadership of the dissertation council in several physical and mathematical scientific areas, organization of deep educational work in the field of preserving historical memory and patriotism, methodological activities aimed at improving the quality of education and research. Materials and Methods: Milestones of Dmitriy A. Usanov’s life path are comprehensively reflected in the article based on the analysis of his diverse and large-scale activities, compiling a bibliography of his main scientific, methodological and educational works. Conclusion: An integral idea of the activities of an outstanding scientist, inventor, teacher, educator of youth is being formed.

The possibility has been explored to control the photonic Tamm resonances (TRs) in the one-dimensional microwave photonic crystal (MPC) with the dielectric filling by changing the thickness of the MPC’s outer layer adjacent to the heavily doped layer of the semiconductor GaAs structure. The controlled photonic TRs have been used to measure the conductivity of the heavily doped semiconductor layer. It has been shown that depending on the conductivity of the layer the specific tuning of the TR frequency is necessary in order to achieve a high sensitivity of the TR to the change of the conductivity. The possibility of observing the plasma resonance in the infrared range has additionally allowed to determine the concentration and mobility of free charge carriers in the heavily doped layer of the GaAs structure.

Background and Objectives: Microwave Bragg structures are used to create various types of microwave devices, including tunable resonators, directional couplers, miniature antennas, matched loads, various types of microwave filters with controlled characteristics. Coaxial Bragg structures based on coaxial elements, which are one of the most common types of microwave elements in waveguide systems, are characterized by a wide frequency range and the absence of radiation losses. Existing coaxial Bragg structures have significant dimensions or require irreversible structural changes to be made in their design. In this article, the opportunity to create a small-sized coaxial Bragg structure on the set of periodically arranged coaxial line segments with different dielectric filling is proposed. Materials and Methods: The transfer matrix of a complex quadrupole, which is a cascade connection of elementary quadrupole with known transmission matrices, was used to calculate the transmission and reflection coefficients of an electromagnetic wave in coaxial Bragg structures. For experimental studies, a measuring section was created in the form of a dismountable segment of the coaxial transmission line including a formed coaxial Bragg structure. Results: Amplitude-frequency characteristics of 11-layer coaxial Bragg structures without defects for different ratios of the electric lengths of the dielectric segments and 19-layer coaxial Bragg structures with the different defect location inside the structure for small 1.4 mm and large 19.26 mm defect lengths have been investigated. Conclusion: The сoaxial Bragg structure can be considered as several embedded in each other Bragg gratings with a different number of cells depending on the ratio of the electric lengths of elementary structural units. The frequency position of the defect mode in the coaxial Bragg structure with periodically alternating dielectric filling almost does not depend on the location of the defect inside the structure but on the electrophysical parameters of the defect. The amplitude of the defect mode is maximum for the defect located in the center of the coaxial Bragg structure.