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Quasioptical THz wave receiver based on the widely accessible pyroelectric detector like PM-4 has been studied. The necessary components (modulator, receiver, preamplifier, synchronous detector, ADC module, and controller) are considered. The NEP of the pyroelectric detector was measured at 140GHz. Also, with the help of the Michelson interferometer, the wavelength measurements have been done. It is shown that the pyroelectric detector together with the mentioned components can be used to solve a number of problems in the THz frequency range, which do not require high sensitivity of the receiver.

The scale model measurements of the field distribution at various distances from the aperture of antennas based on oversized quasioptical waveguides are presented. The goal is to study their characteristics for introducing radiation into the plasma chamber of thermonuclear fusion reactors. It was found that such antennas provide the necessary parameters of the microwave beam (diameter and divergence) without the use of focusing mirrors.

УДК 535.515:621.3.072.7 PACS numbers: 42.25.Lc, 42.25.Bs, 42.70.Mp, 77.84.-s Предмет и цель работы: Исследуется возможность создания широкополосного вращателя плоскости поляризации для длинноволновой части терагерцевого диапазона. Методы и методология: Для достижения поставленной цели были использованы результаты работы, в которой методом поляризационных матриц рассеяния рассмотрены перестраиваемые и широкополосные дифференциальные фазовые секции, состоящие из нескольких двулучепреломляющих элементов. Результаты: Показано, что применение широкополосных дифференциальных фазовых секций позволяет значительно расширить рабочую полосу частот вращателя плоскости поляризации. Заключение: Экспериментальное исследование подтвердило возможность создания широкополосного вращателя плоскости поляризации. В качестве двулучепреломляющих элементов были применены искусственные диэлектрики, обладающие так называемым двулучепреломлением формы. Ключевые слова: квазиоптика, терагерцевый диапазон, вращатель плоскости поляризации, дифференциальная фазовая секция, двулучепреломление Статья поступила в редакцию 20.02.2017 Radio phys. radio astron. 2017, 22(1): 78-85 СПИСОК ЛИТЕРАТУРЫ 1. Радиоволновая эллипсометрия / Конев В. А., Кулешов Е. М., Пунько Н. Н. / Под ред. И. С. Ковалева. – Минск: Наука и техника, 1985. – 104 с. 2. Косяк О. С., Безбородов В. И., Кулешов Е. М., Нестеров П. К. Перестраиваемые и широкополосные дифференциальные фазовые секции в терагерцевом диапазоне частот // Радиофизика и радиоастрономия. – 2016. – Т. 21, № 4. – С. 318–329. 3. Борн М., Вольф Э. Основы оптики / Пер. с англ. С. Н. Бреуса , А. И. Головашкина , А. А. Шубина под ред. Г. П. Мотулевич . – М.: Наука, 1973. – 719 с. 4. Безбородов В. И., Косяк О. С., Кулешов Е. М., Ячин В. В . Дифференциальные фазовые секции на основе двулучепреломления формы в терагерцевом диапазоне частот // Радиофизика и электроника. – 2014. – Т. 5(19), № 3. – С. 92–97. https://doi.org/10.1615/TelecomRadEng.v74.i8.70 5. Безбородов В. И., Косяк О. С., Кулешов Е. М., Ячин В. В. Согласование структур с двулучепреломлением формы со свободным пространством в терагерцевом диапазоне частот // Радиофизика и электроника. – 2015. – Т. 6(20), № 2. – С. 83–89. 6. Кулешов Е. M. Глава 8. Измерения в субмиллиметровом диапазоне радиоволн / Радиоэлектроника и радиофизика миллиметровых и субмиллиметровых радиоволн / Под ред. А. Я. Усикова. – Киев: Наукова думка, 1986. – С. 140–157.

Purpose: Studying the quasioptical tunable and broadband differential phase section (DPS) consisting of several birefringent elements (BE) on the basis of form birefringence effect. Design/methodology/approach: Using the polarization scattering matrix method, the impact of the mutual rotation axis of anisotropy of several BE by the amount of phase shift and the position of the plane of anisotropy of resulting DPS is considered. Findings: The DPS tunable in a wide range are shown to be possibly implemented in the case of quarter-wave DPS of two, and in the case of half-wave DPS of three, identical non-tunable BE. The analysis has shown to the possibility of creating a broadband quarter-wave and half-wave DPS. Сonclusions: Experimental research has confirmed the possibility of constructing a tunable and broadband DPS. On this basis, tunable and broadband polarization converters, rotators of polarization plane, polarization phase shifters and frequency shifters in the terahertz frequency range can be created.

PACS numbers: 81.05.Xj, 78.67.Pt Subject and purpose: The resonant properties are studied of the dielectric metalayer in a form of a doubly periodic structure consisting of silicon parallelepipeds placed on a flat quartz substrate. Design/methodology/approach: Using the pseudospectral timedomain method, numerical simulations of electromagnetic plane wave scattering on the metalayer are made. Resonant properties of the metalayer were experimentally investigated by measuring frequency characteristics of a transmitted electromagnetic wave in a quasi-optical measuring waveguide within 52 to73 GHz. For experimental study, a sample of metalayer was made with the method of mechanical cutting of a layered silicon-quartz structure by a diamond disk. A peculiarity of the studied structure is a double-layer character of the array elements. Each element has a form of a parallelepiped and includes an upper silicon part and a bottom quartz part. A height of the upper part of parallelepiped was changed during the experimental study (the patterned silicon side of the metalayer was polished). Findings: A new technological design of metalayers providing an excitation of high-Q resonances is proposed. The resonances were found to be associated with forming of longitudinal electric or magnetic dipoles in elements of the array and in the substrate. The properties of these kinds of resonances depend on the height of the elements in different ways that allows to control the resonant properties of the structure by selecting the height of the silicon parts. Experimental studies have confirmed the properties of the magnetic dipole resonances predicted theoretically. Conclusions: Performed theoretical and experimental research efforts have demonstrated the opportunity to design all-dielectric resonant metalayers for terahertz applications. Key words: dielectric metalayer, periodic structure, silicon, quartz, transmission resonance, absorption resonance Manuscript submitted 22.12.2015 Radio phys. radio astron. 2016, 21(1): 65-76 REFERENCES 1. AYDIN, K., BULU, I., GUVEN, K., KAFESAKI, M., SOUKOULIS, C. M. and OZBAY, E., 2005. Investigation of magnetic resonances for different split-ring resonator parameters and designs. New J. Phys . vol. 7, id. 168. DOI: 10.1088/1367-630/7/1/168 2. FALCONE, F., LOPETEGI, T., LASO, M. A. G., BAENA, J. D., BONACHE, J., BERUETE, M., MARQUES, R., MARTIN, F. and SOROLLA, M., 2004. Babinet principle applied to the design of metasurfaces and metamaterials. Phys. Rev. Lett . vol. 93, no. 19, id. 197401. DOI: https://doi.org/10.1103/PhysRevLett.93.197401 3. KHARDIKOV, V.V., IARKO, E. O. and PROSVIRNIN, S. L., 2012. Agiant red shift and enhancement of the light confinement in a planar array of dielectric bars. J. Opt . vol. 14, no. 3, id. 035103. DOI: https://doi.org/10.1088/2040-8978/14/3/035103 4. KHARDIKOV, V. V., IARKO, E. O. and PROSVIRNIN, S. L., 2008, Using of transmission matrixes and pseudospectral method in time domain to investigate light diffraction on planar periodic structures. Radio Phys. Radio Astron . vol. 13, no. 2, pp. 146–158 (in Russian). 5. ZHAO, Q., ZHOU, J., ZHANG, F. and LIPPENS, D., 2009. Mie resonance-based dielectric metamaterials. Materials Today . vol. 12, is. 12, pp. 60–69. DOI: https://doi.org/10.1016/S1369-7021(09)70318-9 6. VAN DE GROEP, J. and POLMAN, A., 2013. Designing dielectric resonators on substrates: Combining magnetic and electric resonances. Opt. Express. vol. 21, is. 22, pp. 26285–26302. DOI: https://doi.org/10.1364/OE.21.026285 7. LAMB, J. W., 1996. Miscellaneous data on materials for millimeter and submillimetre optics. Int. J. Infrared Millimeter Waves . vol. 17, no. 12, pp. 1997–2034. DOI: https://doi.org/10.1007/BF02069487 8. KULESHOV, Y. M., 1986. Chapter 8. Measurements in sub-mm wavelength band. In: A. Y. USIKOV, ed. Electronics and Radio Physics of Millimeter and Sub-millimeter Waves . Kyiv: Naukova Dumka Publ., pp. 140–157 (in Russian). 9. The A.Y. Usikov Institute of Radio-Physics and Electronics of National Academy of Sciences of Ukraine, 2008. Quasi-optical radio measuring devices on the basis of a circular hollow dielectric beamguide of submillimeters and millimeters waves [online]. Available from: http://www.ire.kharkov.ua/depquasi/HDB.html

The phase shifter is one of the basic elements of radio measurements systems. The polarization phase shifters with half-wave differential phase section rotating in the field of circular polarized wave rotating between two quarter-wave sections are widely used in waveguide and quasi-optical microwave circuits. The widebandedness of such phase shifters is determined by the widebandedness of the differential phase sections. The broadband differential phase sections composed of several birefringent elements with the planes of anisotropy twisted with respect to each other are used to expand the operating frequency range. Theoretical and experimental studies show the efficiency of the use of the differential phase sections in the polarization phase shifters operating in the THz frequency range.

The resonance properties of the metasurface were obtained using the pseudo-spectral time domain method. The frequency dependence of transmission and absorption of sub-THz waves passed through metasurface have been measured.

In this paper, polarisation scattering matrices are used to investigate the possibility of developing variable differential phase sections (DPS) made of birefringent elements based on the form birefringence effect. The possibility of developing quarter-wave and half-wave differential phase sections variable in a wide frequency range has been shown. Analysis has confirmed the possibility of developing broadband quarter-wave and half-wave DPS. An experimental study in the long-wave part of the THz range has been conducted.

A phase frequency changer (PFC) for quasi-optical transmission line with phase sections made of crystal quartz and polarizers executed on the basis of small-period wire gratings has been considered. The PFC is intended for operation in terahertz (THz) frequency region. It has been examined at the frequency f o= 0.89THz. The influence of the differential phase shift deviation in the sections on the output signal spectrum and the influence of the sections mismatch on the reflection signal spectrum have been considered. In the frequency region ± 10% f o the levels of the spurious spectral components of output signal are less than −40 dB with regard to the level of the useful signal of the shifted frequency. The levels of all spectral components of the reflection signal are less than −60 dB with regard to the level of the useful component of the PFC output signal.

The development of antenna duplexers for transceiving quasi-optical systems of millimeter and submillimeter wavelengths are considered for two groups of devices — passive and active action. Duplexers, using properties of quasi-optical hybrids, belong to the first group, and duplexers on the base of semiconductor or ferrite devices are included to the second group. Results of developments and investigations of considered devices in the millimeter wave range are presented.

Quasioptical reflectometer based on hollow dielectric beamguide (HDB), terahertz beamguide components and elements has been developed. The reflectometer has been analyzed in terms of its application for nondestructive method for surface and subsurface contamination of carbon fiber reinforced plastic (CFRP). Sub-terahertz (0.1…0.2 THz) measurement results of CFRP samples with different surface contaminations are presented.

Transmission of microwave signals under low-losses conditions is highly demanding task in sub-mm EPR and DNP spectroscopy. We have designed and built a quasioptical setup in the Michelson interferometer configuration using oversized metallo-dielectric waveguides (MDW) of a square-shape cross-section and components such as attenuators, beam splitters, wavemeter, tapers to fundamental TE10 mode which have extremely low losses in sub-mm wave range. Following features of the setup such as total transmission losses below 2 dB from the source port to a resonator with a sample inside the cryomagnet; fine balance tuning between signal and reference channels affording up to 36 dB background signal suppression, linear-to-circular polarization conversion with a possibility to tune its phase, which allows effective suppression of reflected signal with respect to induction signal; switching between two microwave sources; and high power handling up to 20 Watt helped to reach high performance of the 9.2 Tesla DNP/NMR/EPR spectrometer. First liquid-state DNP results on nitroxide radicals in water will be presented.

Some quasi-optical measuring devices and components have been developed for integration into THz band circuits. Such devices are based on square 10x10 and 14x14 mm metal-dielectric waveguides designed, respectively, for the 0.176 to 0.410 and 0.110 to 0.260 THz frequency bands. The developed quasi-optical devices and units can complete with comparable long-wave products and outperform them in some cases.

The attenuator on the basis of a hollow metal-dielectric waveguide of square cross-section 10 x 10 mm with similar polarizing gratings has been realized and tested. The largest attenuation of such an attenuator in the range 0.26 THz is 35 dB, attenuation scale reading A=(0...25)dB, initial attenuation is 0.3dB, VSWR is less than 1.05. The attenuator error is plusmn(0.1+ 0.02A)dB.

Quasi-optical phase frequency changer (PFC) with phase sections made of crystal quartz has the level of reflected signal of shifted frequency less than -60dB with regard to the level of transmitted signal in 10% frequency band.

A polarizing phase shifter for quasi-optical transmission line with phase sections made of crystal quartz and polarizers executed on the basis of small-period wire gratings is considered. The phase shifter is intended for operation in terahertz (THz) frequency region. It was examined at 0.89THz frequency (f/sub 0/). The influence of differential phase shift deviation in the sections on the phase shifter error is considered. The error was /spl plusmn/2/spl deg/ in the frequency region which is 15% of f/sub 0/.