Radio physics and electronics

15-32

Authors: I. Ivanchenko, N. Popenko, M. Khruslov, R. Chernobrovkin, S. Radionov, V. Pishchikov

Subject and purpose. This article is devoted to the review of the original works of the authors on studying the effective small-sized individual radiators of various types using near-field technology. Methods and methodology. The research algorithm consists in carrying out numerical modeling of the proposed antenna designs using software packages, creating the appropriate physical prototypes and comparing the results of numerical and direct experiments of such radiator characteristics as bandwidth, radiation pattern, gain and ellipticity. At the same time, a detailed analysis of the spatial near-field distributions gives the necessary information for further optimization of the antennas and obtaining their optimal characteristics. Results. The characteristics of various modifications of monopole, disk, aperture, microstrip and spiral antennas with record characteristics are systematized and analyzed, and the possibility of their use in a compact mobile microwave direction finder and nonlinear locator is also shown. The results of studying the diffraction coupling of individual aperture radiators with the involvement of developed methods of measuring the spatial near-field distributions were used to create a laboratory model of an antenna array. Conclusions. A review of the results of studying the small-sized microwave antennas of various types over the past decade is given. We demonstrate the efficiency of using information on the spatial near-field distributions in the inductive and wave regions of the radiating apertures during the elaboration and subsequent optimization of the main characteristics of both individual original radiators and antenna arrays based on them.

49-56

Authors: M.M. Solovan, P.D. Maryanchuk

Subject and purpose. The subject of research is the electrical and photoelectric properties of the МoN/n-Si heterostructure fabricated for the first time by means of the deposition of thin film of molybdenum nitride (n-type conductivity) by the reactive magnetron sputtering onto single crystal substrates of n-type Si. The purpose of the work is to fabricate the photosensitive MoN/n-Si surface-barrier structures, determine the barrier parameters and dominant mechanisms of current transfer through the obtained heterostructure at direct and reverse biases, investigate the photoelectric properties and causes of losses of photogenerated charge carriers in the obtained heterostructures. Method and methodology. Direct and reverse volt-ampere characteristics of the MoN/n-Si heterostructure were measured at various temperatures, as well as when irradiated with white light with an intensity of Popt= 80 mW/cm2 and three lasers with λ = 405, 646, 780 nm with intensity Iopt = 5 mW cm-2. Results. The obtained heterojunctions with the height of potential barrier φ0 = eVbi = 0.37 еV have pronounced rectifying properties. The dominant current transport mechanisms through the heterojunction under investigation were determined: at forward bias, volt-ampere characteristics are well described within the generation-recombination and tunneling-recombination models with the participation of surface states, and аt reverse bias, they are described within the tunnel model. Conclusion. It was established that when illuminated with white light with the intensity of Popt = 80 mW/cm2, the reverse current Ilight increases compared with its value in the dark Idark by more than an order of magnitude due to the separation of photogenerated electron-hole pairs. The photosensitivity of this heterostructure to monochromatic illumination by lasers with electromagnetic wavelengths λ = 405, 646, 780 nm and intensity Iopt = 5 mW cm-2 is shown. The results obtained allow us to c

68-77

Authors: S.A. Vlasenko, A.V. Degtyarev, M.M. Dubinin, V.A. Maslov

Subject and ppurpose. In this paper, the spatial-energy characteristics of laser beams with inhomogeneous spatial polarization with their moderate and sharp focusing are theoretically investigated. In the numerical simulation of focusing of wave laser beams in the terahertz range, laser resonator modes based on a circular metal waveguide were used as the radiation under study. These modes coincide with the proper types of oscillations of such a waveguide. For the calculation, we selected symmetric and asymmetric modes with azimuthal, radial, and complex spatial polarization of the field. Methods and methodology. In the study of the propagation of the components of the electric field of laser radiation in free space, Rayleigh-Sommerfeld integrals were used in the nonparaxial approximation. The effect of the focusing lens on the radiation under study was taken into account using the function of amplitude-phase correction. The transverse distributions of the total field intensity and its individual components of the studied resonant modes in the region of the minimum size of the focal spot of focused radiation beams were studied. Results. Wave beams with inhomogeneous spatial polarization of radiation are necessary for solving important fundamental and applied problems. These tasks are associated with the interaction of electromagnetic waves of the terahertz range with matter. For example, diagnostics of the surface of materials, thin films, biological objects, THz transmission systems and information processing, the achievement of subwave resolution THz tomography, terahertz communication systems, etc. The results of studies of focusing features in the terahertz range are practically absent. A theoretical study was made of the physical features of moderate and sharp focusing of laser beams of radiation excited by the modes of a resonator with a circular metal waveguide with different spatial polarization of the field. The results obtained extend knowledge of the focusing features of terahertz laser beams. Conclusions. The physical features of the spatial-energy characteristics are established with moderate and sharp focusing in free space of radiation beams with different spatial polarization of the field. These beams were excited by laser resonator modes based on a circular metal waveguide in the terahertz range.

12-23

Authors: Guo Qiang, Luo Yi-yang, V. I. Lutsenko, Zheng Yu

Subject and purpose. Recently, there has been an interest in the use of non-equidistant active phased antenna arrays (AA) in airborne radars to facilitate the aerodynamics of the thermal regimes of their operation. Non-equidistant linear AAs reduce the number of antenna elements without noticeable loss of resolution (accuracy) and at the same time maintain a low level of side lobes. Almost all large antennas of radio telescopes and long-range radars are grids with non-equidistant arrangement of elements and with an unfilled aperture. The aim of this work is to develop new and non-traditional methods for constructing nonequidistant antenna arrays using Latin squares and cyclic difference sets. Results. The possibility of synthesizing large AAs based on the composition of squares using cyclic difference sets (CDS) for the formation of elements of Latin squares is shown. A method for their construction and a synthesis algorithm are proposed. The properties of this type of antenna arrays, which provide a sufficiently low side radiation at a high degree of rarefaction, are studied. The features and main characteristics of such antennas are investigated. Methods and methodology. The algorithm for calculating the coordinates of the antenna arrays using the values of the elements of Latin squares in this case is the same as in the construction of a lattice based on magic squares. It is based on the use of the value of the element of the generating matrix (the formed square) as the basis of the interferometer formed by the neighboring elements. The directivity patterns of the AAs were studied and the side lobe levels of the resulting non-equidistant antennas were estimated. Conclusions are made about the novelty of the proposed concept of constructing non-equidistant antenna arrays on the basis of Latin squares accepting the CDS as elements and its advantages in comparison with known methods. The possibility of synthesizing large antenna arrays on the basis of the composition of squares using the CDS for forming elements of Latin squares with small filling and redundancy coefficients and permissible values of lateral radiation is shown. In terms of characteristics, they are better than non-equidistant two-dimensional lattices, used up to the present time, constructed only on the basis of cyclic difference sets. The characteristics of the obtained lattices are studied. It is shown that the use of the Latin square, using the CDS as elements in the synthesized matrix, significantly improves its characteristics, and also provides a more flexible variation of the design parameters(v, k, l).

33-46

Authors: A. P. Nickolaenko, Yu. P. Galuk, M. Hayakawa

Subject and purpose of the work. In the present work, the perturbations are simulated of the amplitude of the vertical electric and horizontal magnetic fields of global electromagnetic (Schumann) resonance caused by the local ionosphere disturbance over the earthquake center with an account for the day–night non-uniformity. The source and the receiver are located at the same meridian symmetrically with respect to the equator at the points with coordinates 22.5° N and 22.5° S respectively. Position of the propagation paths is fixed relative the morning terminator: on its night (60° E) or the dayside (120° E). Variations of the amplitudes perturbation of the fields are considered when the localized non-uniformity moves along or across the propagation path. Methods and methodology. To determine the propagation parameters of extremely low frequency (ELF) radio waves, the full wave solution is used, which leads to the solution of the Riccati equation. The spectral components of the fields are found numerically using the two-dimensional telegraph equation. The results of the work. Numerical estimates are obtained of the influence of the local non-uniformity of the ionosphere on the amplitude of the electric and magnetic fields at different frequencies in the global electromagnetic (Schumann) resonance band for different positions of disturbance relative the propagation path located at the night or the dayside of the morning terminator. Conclusion. The influence of localized non-uniformity on the field amplitude increases with frequency. Field modifications in the presence of a local disturbance are of the interference nature due to interaction of the direct and the reflected from the local inhomogeneity radio waves. The day-night regular non-uniformity of the ionosphere plays a minor role and its influence might be neglected.

58-68

Authors: D. M. Glibitskiy, O. A. Gorobchenko, O. T. Nikolov, T. A. Cheipesh, T. N. Dzhimieva, I. S. Zaitseva, A. D. Roshal, A. M. Zibarov, A. V. Shestopalova, M. A. Semenov, G. M. Glibitskiy

Subject and purpose. In this paper, we studied the relationship of the structural and aggregation state of biopolymers with the quantitative characteristics of the textures of the films formed during the drying of biopolymer solutions. Methods and methodology. The structural changes of the biopolymer were determined by IR, UV and fluorescence spectroscopy, the size and surface potential of biopolymer particles were determined by dynamic light scattering, the state of the water environment was determined by microwave dielectrometry. To obtain films, saline solutions of calf thymus Na-DNA, bovine serum albumin (BSA) or human serum albumin (HSA) were dried in a glass cuvette under thermostatically controlled conditions. For the numerical characterization of textures, the relative area, fractal dimension and characteristics of zigzag patterns were used. Results. The paper presents a mini-review of the results during the development of a method for assessing the influence of biologically active substances (inorganic and organic) and physical factors (temperature and gamma irradiation) on biopolymers by the changes in texture parameters. It is shown that the formation of zigzag structures is sensitive to the structural and aggregation effects of biologically active substances and physical factors, and requires the presence of chloride ions. Conclusion. A method for assessing the influence of the corresponding factors by the changes in texture parameters is proposed. The presented results clarify the role of biopolymer, as well as salt cations and anions, in the formation of textures (in particular, zigzag structures) on the surface of films, and show the relationship of structural changes and aggregation of biopolymer with quantitative characteristics of zigzag patterns.

15-36

Authors: A. А. Barannik, A.І. Gubin, A. А. Lavrinovich, N. T. Cherpak

The subject and purpose of the work. A review of the main results obtained by the authors in the process of microwave (MW) research of unconventional superconductors and the development of MW devices based on cuprate high-temperature superconductors (HTS) over the past 10–15 years is presented. Methods and methodology of work. Experimental studies were carried out by the methods of impedance measurements of superconducting samples. To this end, the authors developed two measurement techniques in the mm wavelength range: based on quasi-optical sapphire resonators and using the feature of reflection of a p-polarized wave from the surface of a superconductor at grazing angles of incidence. The results of the work.. The epitaxial films of the cuprate YBa2Cu3O7–d superconductor and Fe-containing superconductors in the form of single crystals of pnictide Ba (Fe0.926Co0.074)2As2 and epitaxial films of chalcogenide FeSexTe1–x (x = 0.5 and 0.7) are investigated. The results of the MW response of the electrodynamic structures with the samples under study served as the basis for finding the complex conductivity, including fluctuation one, and physical quantities related to it. In general, the results obtained confirm the scenario of d-wave symmetry of the gap function for cuprate superconductors and s±-wave symmetry for Fe superconductors. However, a number of detected features and effects, namely, an unusual frequency dependence of the residual surface resistance in YBa2Cu3O7–d in the form of w3./2, the growth of quasiparticle conductivity with decreasing temperature, starting from the critical one, as well as the avalanche-like transition from the superconducting to the strongly dissipative state in the nonlinear coplanar transmission line, require further study. New MW devices based on cuprate HTS films in the mm wavelength range have been developed and created: 1) a quasi-optical sapphire resonator with a radial gap and HTS end walls for studying Fe – superconductors in the form of small (1–2 mm in the plane a–b) samples; 2) planar quasi-optical resonator; 3) a band-pass filter with an E-plane insert in a cross-shaped waveguide. The possibility of contactless testing at room temperature of the homogeneity of the properties of massive superconductors is also shown. Conclusion. The temperature dependence of the complex conductivity of YBa2Cu3O7–d, Ba (Fe0.926Co0.074)2As2 and FeSexTe1–x (x = 0.5 and 0.7) superconductors and physical quantities related with it was obtained, which allows us to judge the confirmation of the corresponding wave symmetry scenarios of gap function function in the investigated superconductors. However, a number of detected features and effects require further study. The previously expressed assessment of the possibility of creating passive HTS-based MW devices with operating frequencies up to 40 GHz has been experimentally confirmed.

55-66

Authors: S. S. Apostolov, D. V. Kadygrob, Z. A.Маizelis, T. N. Rokhmanova, A. A. Shmat’ko, V. A. Yampol’skii

Subject and purpose. In this review the propagation of electromagnetic waves localized near the boundary of a sample of a layered superconductor with layers either parallel or perpendicular to its surface is discussed. The results obtained in a number of papers studying the dispersion law for such waves are generalized, classified and supplemented. Due to the strong anisotropy and nonlinearity of the Josephson plasma in layered superconductors, localized waves can have unusual dispersion properties, and their excitation can be accompanied by unusual resonance phenomena. Methods and methodology. The electromagnetic field in a layered superconductor is determined by the distribution of the gauge-invariant phase difference of the order parameter, which satisfies the system of coupled sin-Gordon equations. Based on the solution of these equations, as well as the Maxwell equations in the dielectric environment, dispersion relations can be obtained for localized electromagnetic modes. Results. In samples of a layered superconductor, whose layers are parallel to its boundary, both surface waves and waveguide modes with normal dispersion can propagate. For samples, the layers in which are perpendicular to the boundary, the dispersion law depends on the angle of propagation of the waves relative to the superconducting layers. In this paper it is shown for the first time that waves localized in a layered superconductor plate have an anomalous dispersion for all directions of propagation, except propagation strictly along the layers. Dispersion curves for such waves can have points of maximum and/or minimum, which can lead to nontrivial effects (e.g., stopping of light or internal reflection). Also, the excitation of localized waves and the unusual resonant phenomena are discussed in the work. Conclusions. Due to the strong anisotropy and nonlinearity of the layered superconductor, the dispersion laws for waves, localized both in semi-infinite samples and in plates have a number of interesting features that lead to new phenomena important for using in the physics of the terahertz range.

95-107

Authors: S.V.Nikolaev, V.V.Pozhar, M.I.Dzyubenko, K.S. Nikolayev

Subject and purpose. This article is devoted to a brief review of the main results of the research cycle aimed at developing solid active media based on dye-activated polyurethane compounds. The ultimate goal of these studies was the creation of solid-state active elements that make it possible to realize a wide-band solid-state dye laser (SSDL), which emits frequency-tunable radiation with a microsecond pulse duration. Methods and methodology. The problem was solved mainly by experimental methods. At the same time, the studies carried out included a full range of works, starting with the production of samples of solid-state active media to study the generation characteristics of the active elements created. Results. In the course of the work, laser-active media based on industrial polyurethanes of various grades activated with Rhodamin 6G, Sulforhodamine 101, Oxazin 17, and Oxazin 1 dyes have been created and their spectral-luminescent characteristics have been studied. Experimental samples of laser matrices are made. The optical properties of the media created are studied and the influence of the technique of making samples on the nature of possible distortions of their optical homogeneity is determined. The emission ability of polyurethane matrices was studied. With transverse monochromatic excitation laser emission was obtained on polyurethane matrices with an efficiency of 12 to 26% and energies from 23 to 127 mJ. Radiation resistance and possible service life of polyurethane media have been investigated The thermo-optical properties of polyurethane active media and their effect on the directivity of SSDL radiation are studied. The effect of induced birefringence, which occurs under conditions of asymmetric pumping of microsecond duration, is observed. It was found that under such conditions, polyurethane active elements emits polarized radiation even when excited by depolarized light. A possibilities of narrowing and tuning the emission spectrum of polyurethane matrices in dispersion resonators with angular and amplitude type of selection are investigated. The laboratory model of a tunable SSDL with replaceable polyurethane laser elements, generating a pulsed radiation of a microsecond duration in the spectral range of 565...700 nm is created and tested. Conclusions. The results of the performed studies allow to conclude that industrial polyurethane compounds can be successfully used as solid media for active elements of SSDL.

9-39

Authors: V. D. Yeryomka, O. F. Pishko

Subject and purpose. In the vacuum microwave electronics, with increasing the operating frequency of the source electromagnetic oscillations, most attention is paid to increasing the efficiency of electron-wave interaction on the Vavilov-Cherenkov effect of rectilinear electronic flows with a slow spatial harmonic of electromagnetic waves in metallic periodic slowing structures (PSS). At the same time, isufficient attention was paid to the study of the effect of the coefficient of the use of rectilinear electronic flows on the frequency energy Cherenkov oscillators and amplifiers of electromagnetic oscillations. Clinotron effect, reveated in 1956 in the process of development and research of O-type backward wave tubs (O-type BWT) of short-wave ranges Institute for Radiophysics and Electronics of Academy of Sciences of the Ukrainian SSR, demonstrated a significant influence of the utilization factor of a spatially developed rectilinear electronic flows on the frequency-energy characteristics of the O-type BWT. Methods and methodology. There is no publication in the scientific literature that summarizes the results of research into the frequency-energy characteristics of vacuum sources of terahertz (THz) electromagnetic oscillations with spatially developed electron currents, created during the last 50 years and differing in the principle of action, by theoretical and experimental methods of influence of the clinotronic effect on the frequency-energy characteristics. Results. The analysis of the frequency-energy characteristics of THz BWT-clinotrons, THz-clinoorotrons, THz-gyroclinotrons, THz-clinoorbictrons was carriedout. Based on the analysis of the results of the research, there is a conclusion about the existence of a close relationship between the value of the coefficient of the use of spatially-developed electron flows and frequency-energy and also the mass-size characteristics of vacuum sources of THz electromagnetic oscillations. Сonclusions. The use of the clinotronic effect in vacuum sources of electromagnetic oscillations with spatially developed electron currents contributes to the creation of compact generators and signal amplifiers in the "THz slit" of the spectrum of electromagnetic oscillations.

65-76

Authors: O. I. Kovalenko

Subject and purpose. Particularities of the targeted modification of functionals of the wheat seeds state by irradiation with a low-intensity electromagnetic field (EF) were investigated. The aim of the work was to investigate the effectiveness of low-intensity electromagnetic field mediated by water on wheat seeds depending on their initial state, evaluated statistically as “norm” and “pathology”, and to study the possibility of functional reconstruction of the wheat seeds with the “pathology” state. Methods and methodology. The work is experimental. Approved radio-physical, radio-technical, biological methods and techniques were used in this work. Generators Г4-141 (37.5…53.57 GHz) and Г4-142 (53.57…78.33 GHz) were used for electromagnetic field irradiation. Efficiency of the electromagnetic field influence was evaluated using functionals of the seed state: energy of growing, average length of roots and seedlings in each portion. Statistical methods were used in the processing and the analysis of the obtained results. Results of work. The possibility of a targeted modification of the functional parameters of wheat seeds upon their interaction with water, previously irradiated with EF, was established. Differences in the effectiveness of the water-mediated influence of EF depending on the frequency and exposure of the signal were shown. We found the dependence of biological reaction of the wheat seeds on the electromagnetic field irradiation mediated by water. The reaction depends on the initial state of the seeds: those in the “norm” state get oppressed, while those in the “pathology” state are stimulated. The application of water-mediated electromagnetic field influence on wheat seeds in the “pathology” state was shown to be promising for restoring of the lost functional properties. Efficient regimes of electromagnetic field influence mediated by water were established. Conclusion. Water-dissipative model of the electromagnetic field interaction with substance was confirmed. Method of the electromagnetic field influence mediated by water on wheat seeds was proposed. It allows stimulating their lost properties, which is promising for development of agricultural technologies.

9-21

Authors: V. V. Ovsyanikov, E. R. Beznosova

Subject and Purpose. The results of studies of actual methods for expanding the frequency range of vibrational curved whip and loop antennas, and antenna arrays based on them are presented. Optimal designs of broadband antennas with the concentrated reactive loads included in the shoulders are considered. Methods and methodology. Calculations of the electrical parameters of the antennas were performed by the integral equation method, which allowed us to investigate new variants of broadband pin and loop antennas and antenna arrays more deeply. Two types of antennas are investigated, which are promising for the use in the microstrip implementation in the form of single antennas and as part of antenna arrays. The first variant is a Z-shaped antenna of orthogonal linear polarization, supplemented by concentrated capacitive loads; the second one is a loop in the form of a frame also with capacitive loads. To approximate the actual application conditions, the antenna parameters were determined when they were placed at a small height above the conductive screen (plane). Results. As a result of calculations of the electrical parameters of Z-shaped antennas with capacitive loads and antenna arrays based on them in the wide frequency range of 0.9...1.2...2.7 GHz, we obtained a significant improvement (decrease) in the standing wave voltage coefficient up to values not exceeding five in comparison with similar antennas without loads, for which the values of this parameter reach thirty or more. Compared with conventional rectilinear antennas of the same length and thickness of the rod, the antenna gain factor with loads increased from 7.8 to 9.8 dB at a decrease in the standing wave voltage coefficient from 3.5 to 3.1 at the middle frequency of the investigated range. For loop antennas with capacitive loads, the values of the standing wave voltage coefficient were not more than five in the same range, and at the middle frequency of the range these values did not exceed 1.9, while in antennas without loads this parameter is much higher (up to thirty) and at the middle frequency of the band has a relatively high value up to 15. Coplanar linear in-phase antenna arrays of three Z-shaped and three loop antennas with capacitive loads have been investigated. It is shown that due to the difference in the conditions for the mutual arrangement of the antennas in the gratings, the standing wave voltage coefficient of the terminal array antennas differs from this parameter of the average antenna. Conclusions. To obtain the operating mode of a current close to the traveling wave mode in Z-shaped and loop antennas and antenna arrays based on them, and, as a consequence, to reduce the frequency dependence of the input parameters and radiation patterns of these antennas, it is sufficient to include no more than four capacitive loads in the symmetric antenna arm. This makes it possible to simplify broadband antennas and save the expenses of time and resources for their development and fabrication in comparison with the known works, where it was proposed to include several tens of capacitive loads in the antenna arm.

39-47

Authors: O. V. Sytnik, G. P. Pochanin, S. A. Masalov, V. P. Ruban, P. V. Kholod

Subject and Purpose. The subject of the study is a measuring system consisting of several spatially separated receiving points and a transmitter emitting video pulse signals. The aim of the work is to create an effective algorithm for processing signals from a multi-position observation system under conditions of correlated jamming to solve the problem of the operational detection of mobile objects hidden behind optically opaque obstacles. Methods and methodology of work are based on the difference-distance-measuring principle of calculation of the target coordinates. The informative signal from the target is not identified by direct methods because of the multiple reflections of the sounding signal from the walls of the room and objects located inside it. The procedure for suppressing the interference reflections of the probing signal is developed. The accumulation of a signal and the removal of interference is carried out in real time by subtracting the alternating samples of the observed process from the signals of each receiving point assuming that the object is slow moving or practically unmoving during the time of sounding signal propagation from transmitter to target and back. The delay of the probing signal during its propagation from the transmitter to the target and from the target to each of the receivers has been estimated using the proposed peak factor criterion. The same criterion is used to reject the struck lines on the radar image of the target's trajectory. Results. A high-speed algorithm is developed which, at the condition of a relatively high signal-to-noise ratio, makes it possible to use the signal peak factor as a criterion for jammers suppression at the radar's image. The simplicity of signal processing allowed to continuously display the data in a user-friendly form. The continuity of measurements of the delays of the reflected signals from the target to the receiving points is ensured by polynomial approximation of the object trajectories relative to each of the receivers. Conclusions. The high energy characteristics of the observation system, the stability of the parameters during the measurements, and the high accuracy of the reflected waveform reproduction allowed us to use digital signal processing methods in real time. The simulation results are confirmed by data that were accumulated and averaged over a series of similar experiments.

54-60

Authors: N. N. Beletskii, S. A. Borysenko

Subject and purpose. The effect of reflectionless transmission (tunneling) of electromagnetic waves through the three-layer structure containing a negative-permittivity layer is of great importance both for studying the fundamental properties of solids and for developing new types of unique technical devices. There is a need for investigation of the effect of reflectionless transmission of electromagnetic waves through the three-layer structure containing a negative-permittivity layer in a wide range of the three-layer structure parameters. Methods and methodology. A new approach based on the use of dimensionless thicknesses of a three-layer structure is presented. This approach makes it possible to study the effect of reflectionless transmission of electromagnetic waves for different wavelengths and different values of parameters of the three-layer structure with asymmetric dielectric surroundings. Results. It is shown that the presence of a negative-permittivity layer in the three-layer structure leads to a significant softening of limitations on the parameters of the positive-permittivity layers. Thus, the effect of reflectionless transmission of electromagnetic waves takes place at any preassigned positive value of the permittivity of the layers surrounding symmetrically the negative-permittivity layer. In this case, the parameters of the negative-permittivity layer should be chosen as required. Conclusions. The results of the research extend knowledge on the mechanisms of electromagnetic waves tunneling through the three-layer structures containing negative-permittivity layers. This effect can be used for development of new types of high-frequency solid-state devices operating in different wavelength ranges

69-75

Authors: M. I. Dzyubenko, Y. E. Kamenev, V. P. Radionov, Z. Y. Litvina

Subject and purpose. The terahertz frequency range currently attracts much attention due to the wide possibilities of its application for solving a number of problems in science, technology, and medicine. In this range, metal gratings with the period shorter than the wavelength are widely used as partially transparent mirrors of lasers and in various quasi-optical devices. The determination of the parameters of such gratings is an actual problem. Methods and methodology. The method of experimental comparison of the parameters (losses and transmittance) of metal gratings consisting of parallel conductors is presented in the paper. A THz laser with a smooth adjustment of the output of laser radiation from the resonator was used as a measuring device. The investigated metal grating serves as the exit mirror of this laser. The dihedral 90° mirror is the second mirror of the laser resonator. The adjustment of feedback is performed by rotation of the dihedral mirror around the resonator axis. The angle of rotation of the dihedral mirror, which provides the maximum power of laser radiation, characterizes the transmittance coefficient of the investigated grating. The value of the maximum power of laser radiation characterizes the magnitude of the losses in the investigated grating. This allows one to compare the grating parameters experimentally without the use of metrological instruments. Results. An experimental comparison of the parameters of metal gratings with different structures was carried out as an approbation of the method. Recommendations for the increase of the measurement reliability and further advancement of this method were developed. Conclusions. The proposed method is an effective tool for comparing the transmittance and loss factors in one-dimensional metal gratings for their control and culling. In addition, this method can serve as a measuring device, when reference gratings with known parameters are used for comparison.