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The measurement of a microwave beam focus location was performed to validate theoretical results obtained previously using the quasioptical framework. The system in question is a preliminary set-up of a double reflector system designed for wireless power transfer studies. A very approximate value was achieved but the slight differences verified must be taken into account for the complete system experiment.

The design, simulation, and characterization of a quasioptical system for submillimeter-wave quantification of corneal thickness and water content are presented. The optics operate in the 220-330 GHz band and are comprised of two, custom aspheric, biconvex lenses in a Gaussian beam telescope configuration. The design produces broadband wavefront curvature matching to 7.5 mm radius of curvature target surfaces thus emulating a plane-wave-on-planar-media condition and enabling application of stratified medium theory to data analysis. Aspheric lens coefficients were optimized with geometric ray tracing subject to optical path length penalties and physical-optics simulations showed aspheric designs achieved wavefront coupling to spherical surfaces, superior to equivalent, canonical hyperbolic lenses. The fabricated lens system was characterized in a planar near-field scanner system and demonstrated good agreement to physical-optics simulations. An average central corneal thickness of 652 μm and free water contentvolume of 47% were extracted from ex vivo sheep corneas via complex s-parameters and agree with literature values. Extracted contact lens thickness and water content agreed with independently validated values. Moreover, the quasioptical system enabled observation of dynamic changes in artificial tear-film, thickness, and water content. This work elucidates two major findings related to submillimeter-wave wavefront matching on spherical surfaces, with wavelength order radii of curvature: 1) An asphere whose sag coefficients are optimized via field phase variation on a spherical surface produces coupling superior to a plano-hyperbolic lens. 2) For most feasible apertures, the Gaussian beam waist is located in the aperture near field, suggesting consideration for operating in the beam near field.

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.

We propose an alignment strategy for millimeter spectroscopy of cornea that uses imaging to screen for sufficient alignment conditions. The performance of different corneal imaging objectives, in the presence of misalignment, is evaluated. The cornea is illuminated with a TEM00 Gaussian beam at 650 GHz and the beam is swept across the cornea. Images are generated by calculating the coupling between illumination and scattered beams for each illumination beam position and angle. The cornea is displaced at intervals of 500 microns in the transverse and axial directions and with new coupling coefficient maps generated at each misaligned position. Contrast in the misaligned cases are compared to the aligned case via zero normalized spatial cross correlation. The results show a maximum normalized cross correlation of 0.92 for a two-mirror scanning system and 0.74 for a one-mirror scanning objective. The analysis suggests that imaging contrast at 650 GHz can be used to screen for misalignment that would be difficultto detect with MMW.

in this paper, a novel Frequency Selective Surface (FSS) with polarization staggered bands is proposed. The beams in orthogonal polarization of different frequency bands are divided into a group and transmitted the FSS. The rest are divided into another group and are reflected by the FSS. The FSS with polarization staggered bands is good at separation the bands with narrow transition zone, which realizes transmission and reflection of the incident waves in four different physical mechanisms. What is more, a new frequency separation scheme in quasi-optical feed system is discussed. The FSS with polarization staggered bands, which separate two bands near 90GHz and 108GHz, is fabricated and tested. The reflection coefficient of TM polarization is about 1dB, and the transmission and reflection coefficients in the other band or polarization are less than 0.6dB.

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.

The most critical condition for performing Dynamic Nuclear Polarization (DNP) is achieving sufficiently high electronic B(1e) fields over the sample at the matched EPR frequencies, which for modern high-resolution NMR instruments fall into the millimeter wave (mmW) range. Typically, mmWs are generated by powerful gyrotrons and/or extended interaction klystrons (EIKs) sources and then focused onto the sample by dielectric lenses. However, further development of DNP methods including new DNP pulse sequences may require B(1e) fields higher than one could achieve with the current mmW technology. In order to address the challenge of significantly enhancing the mmW field at the sample, we have constructed and tested one-dimensional photonic band-gap (PBG) mmW resonator that was incorporated inside a double-tuned radiofrequency (rf) NMR saddle coil. The photonic crystal is formed by stacking ceramic discs with alternating high and low dielectric constants. The thicknesses of the discs are chosen to be λ/4 or 3λ/4, where λ is the wavelength of the incident mmW field in the corresponding dielectric material. When the mmW frequency is within the band gap of the photonic crystal, a defect created in the middle of the crystal confines the mmW energy, thus forming a resonant structure. An aluminum mirror in the middle of the defect has been used to split the structure in order to reduce its size and simplify the resonator tuning. The latter is achieved by adjusting the width of the defect by moving the aluminum mirror with respect to the dielectric stack using a gear mechanism. The 1D PBG resonator was the key element for constructing a multi-resonant integrated DNP/NMR probehead operating at 198 GHz EPR / 300 MHz (1)H / 75.5 MHz (13)C NMR frequencies. Initial tests of the multi-resonant DNP/NMR probehead were carried out using a quasioptical 200 GHz bridge and a Bruker Biospin Avance II spectrometer equipped with a standard Bruker 7 T wide-bore 89 mm magnet parked at 300.13 MHz (1)H NMR frequency. The mmW bridge built with all solid-state active components allows for the frequency tuning between ca. 190 to ca. 198 GHz with the output power up to 27 dBm (0.5 W) at 192 GHz and up to 23 dBm (0.2 W) at 197.5 GHz. Room temperature DNP experiments with a synthetic single crystal high-pressure high-temperature (HPHT) diamond (0.3×0.3×3.0 mm(3)) demonstrated dramatic 1,500–fold enhancement of (13)C natural abundance NMR signal at full incident mmW power. Significant (13)C DNP enhancement (of about 90) have been obtained at incident mmW powers of as low as

In a number of previous papers authors have introduced quasiparticle of radio- and optical systems. We have called this quasiparticle by ‘radion’. The basis for this is the representation of Green’s function of equation of quasioptics by Feynman integral. It means that radion has quantum mechanical properties. In particular in approximation of quasioptics one can interprete amplitude of electromagnetic field as amplitude of probability of radion. In the paper presented we describe new features of radion which we have established recently namely we have found some exact solutions of evolutionary equation for field of quantum mechanical averages of momenta of ensemble of radions possessing by average of momentum in initial state depending on average of coordinate in it. We demonstrate three the simplest solutions from this set of exact solutions. These solutions in the form of power series on dimensionless time are applicable up to the moment of gradient catastrophe. For representation of solutions of parabolic equation in approximation of quasioptics Remizov method of quasi-Feynman formulae has been used. All these results due to suggested by us physical analogy are valid for free one-dimensional nonrelativistic quantum mechanical particle too. Also in the framework of Remizov method a number of new formulae for statistical radiophysics and optics has been obtained. ‘Natural’ fractality of radio- and optical systems has been discussed.

This paper is devoted to research and development into sub-THz quasioptical devices and circuits which have been developed in the IRE NAS of Ukraine.

The quasioptical theory is generalized for approximate analytical description of refraction and diffraction focusing of multimode beams of narrowband pulse radiation in oceanic waveguides stratified over depth. General regularities of joint manifestation of spatial focusing and dispersion-induced compression of frequency-modulated pulsed signals during propagation of multimode beams are analyzed.

The “cumulant” method for solving problems of radiation propagation in randomly inhomogeneous media is described. Integral expressions for statistical moments of the wave complex amplitude in general form with the Feynman representation of Green’s function of the quasioptics parabolic equation have been obtained in the framework of the “cumulant” method. It was shown that taking into account some approximation of the processes of radiation multiple scattering in the “cumulant” method allows us to obtain expressions for statistical moments of intensity to an accuracy sufficient to restore the lognormal distribution function.

Knowledge of the interstellar medium (ISM) is essential to understand the stellar life cycle, beside others. The ISM can be traced by the emission or absorption lines of molecules, atoms and ions. Different molecules/atoms/ions trace different phases of the ISM, and some important molecules/ions/atoms can only be detected at frequencies above 1 THz. On sub-millimeter telescopes, heterodyne receivers are generally used for line observations. During my PhD, I built and characterized a 2.6 THz heterodyne receiver. This operating frequency of 2.6 THz is one of the highest reached by recent heterodyne receivers, and in order to characterize and improve this receiver, I focused on 3 important aspects:1) The stability of the receiver, which determines the optimal integration time of the receiver before it has to be recalibrated.2) The design and test of a Martin-Puplett interferometer which allows to superimpose the local oscillator signal and the observed signal with a very good efficiency.3) The design, simulation and characterization of a new kind of phase grating (The Global phase grating) able to efficiently split the local oscillator beam into several beams, which allows the development of a multi-pixel heterodyne receiver.In conclusion, the work accomplished during this PhD constitutes an important step toward the realization of a very stable and highly sensitive 2.6 THz multi-pixel heterodyne receiver using a Martin-Puplett interferometer diplexer, for the next generation of sub-millimeter/farIR space missions., La connaissance du milieu interstellaire (MIS) est essentielle pour comprendre le cycle de vie des étoiles. Le MIS peut être tracé par les raies d'émission ou d'absorption de molécules, d'atomes ou d'ions. Différents ions/atomes/molécules tracent différentes phase de du MIS, et d'importants ions/atomes/molécules peuvent seulement être détectés à des fréquences supérieures à 1 THz. Dans les télescopes submillimétriques, des récepteurs hétérodynes sont généralement utilisés pour les observations de raies spectrales.Durant ma thèse, j'ai travaillé sur la construction, la caractérisation et l'amélioration d'un récepteur hétérodyne à 2.6 THz. Cette fréquence d'observation (2.6 THz) est l'une des plus hautes atteintes par les récepteurs hétérodynes THz existant actuellement, et dans le but de caractériser et d'améliorer ce récepteur, je me suis concentré sur trois aspects essentiels :1) La stabilité du récepteur qui détermine le temps optimal pendant lequel le récepteur peut intégrer un signal avant de devoir être recalibré.2) Le développement d'un interféromètre de Martin-Puplett pour permettre la superposition du signal de l'oscillateur local et du signal observé, avec très peu de pertes.3) La conception, la simulation et la caractérisation d'un nouveau type de réseau de phase (le Réseau de phase global) permettant de diviser efficacement le faisceau de l'oscillateur local en plusieurs faisceaux pour permettre la construction d'un récepteur hétérodyne multi-pixel.Finalement, le travail accompli durant cette thèse constitue une étape importante vers la réalisation d'un récepteur hétérodyne multi-pixel à 2.6 THz utilisant un interféromètre de Martin-Puplett comme diplexeur et possédant de très bonnes caractéristiques de stabilité et de sensibilité, pour la prochaine génération de télescopes submillimétriques spatiaux.

This paper presents a novel THz optical design that allows the acquisition of THz reflectivity maps of in vivo cornea without the need for a field flattening window and preliminary imaging results of in vivo rabbit cornea. The system’s intended use is to sense small changes in corneal tissue water content (CTWC) that can be precursors for a host of diseases and pathologies. Unique beam optics allows the scanning of a curved surface at normal incidence while keeping the source detector and target stationary. Basic system design principles are discussed and image sets of spherical calibration targets and corneal phantom models are presented. The presented design will enable, for the first time, non-contact THz imaging of animal and human cornea.

The Airborne Millimeter- and Submillimeter Observing System (AMSOS) is a total-power radiometer for observations of the 183.3-GHz water vapor rotational line, operated onboard a Learjet aircraft of the Swiss Air Force. The radiometer is also used to observe the 175.45-GHz ozone line in the other sideband. The neatly designed quasi optics provide a regular and narrow output beam with a half-power beam-width angle of 1.2/spl deg/ and efficient sideband switching. A /spl lambda//4-quasi-optical isolator is used for baseline reduction securing attenuation of internal reflections by more than 30 dB. A low noise temperature of the ambient-temperature-operating system (1900 K) and excellent target pointing (better than 0.1/spl deg/) provide a good duty cycle and reliable calibration. A reliable control over the radiometer's operational parameters, like system stability and system temperatures, and higher automatization were required to come up with high demands of an onboard operation. The measured spectra look typical for the region and time where they were observed.

In this paper, we show that the phenomenon of extraordinary transmission through arrays of subwavelength holes, present in the optical regime, is also present in the millimeter wave range. After presentation of the theoretical foundations of the enhanced transmission, measurements of the transmission response have been performed on different samples by using a millimeter wave quasioptical vector network analyzer in the range between 45 and 110 GHz. The prototypes have been fabricated in Aluminum plates with several thickness and different hole diameters drilled by using a laser machine. Good agreement between theory and experiment is obtained, with clear signals of the existence of resonant transmission at wavelengths close to the period of the array. Possible applications in frequency selective surfaces and near-field imaging are envisaged.

A generalized scattering matrix (GSM) approach, which utilizes finite-difference time-domain (FDTD) with a modified unsplit PML (perfectly matched layer) and mode matching techniques, is used to analyze spatial power combiners/dividers with hard horn feeds. The simulation results are experimentally verified for a 1:9 spatial power dividing system. Furthermore, the effects of various design parameters on the overall performance of a 1:9 divider is investigated.

In recent years, electron paramagnetic resonance (EPR) has been extended to high magnetic fields requiring superconducting magnets, by analogy with similar extensions in NMR some decades earlier. One major difference between high-field EPR and NMR is that the corresponding increase in applied resonant frequency has required a significantly different technology in the case of EPR. In contrast to the waveguide-based systems used in conventional EPR fields, high-field EPR has required quasioptical technology that is more commonly used in radioastronomy and communications. This article presents an overview of quasioptical methods as they have been applied in high-field EPR systems. Two matrix methods for designing and engineering quasioptical circuits are presented, and their application illustrated with practical examples. Methods for evaluating the performance of the magnet and sensitivity of the quasioptics are also surveyed. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 22B: 15–36, 2004.

This paper is about the early quasioptics of near-millimeter and submillimeter waves in IRE-Kharkov (Institute of Radio Physics and Electronics of the National Academy of Sciences of Ukraine) and the development of the hollow dielectric beam-waveguide (HDB) technology and measuring techniques of the near-millimeter and submillimeter wavelength ranges, with main application in hot plasma diagnostics. It presents the details of the development based on the declassified reports and the interviews of Y.M. Kuleshov and another key member of the quasioptics (QO) team, M. S. Yanovski. Y.M. Kuleshov and his team had already accumulated rich experience in developing waveguide measuring devices in the whole millimeter-wave range between 1954 and 1961. In 1994-1996, the research project "Ozero" was carried out with Y.M. Kuleshov as a principal investigator. The aim of the "Ozero" was to explore the feasibility of developing a kit of HDB-based measuring devices in the wavelength range /spl lambda/ = 0.7 to 1.7 mm. After the finish of "Ozero", in 1968-1971, the next R&D project called "Oliva" was granted by the same directorate of MRI. Its idea was to dwell on and refine the polarization principles in the measuring circuits for /spl lambda/ = 0.5-0.8 mm. HDB was patented only in 1969. Since the 1970s, the activities of the QO department were focused entirely on the development of HDB-based instruments and systems. Here, the major application area was hot plasma diagnostics in new large Tokamaks. They also dwelled in the development of the measuring techniques including reflectometry and polarimetry. Other HDB based systems elaborated in IRE include radars in the 1970-1980s and RCS testing ranges in the 1990s.

(Sub)Millimeter-telescopes are often used to observe the interstellar medium in the universe and they enable us to study the stellar life cycle. To detect and study some important molecules and ions, we need receivers able to observe at frequencies above 1 THz. Receivers working at such high frequencies are quite new and the 2.6 THz heterodyne receiver I built and characterized during my PhD represents the state-of-the-art of THz heterodyne receivers. I especially focused on three important aspects of this receiver: its stability, the superimposition of the local oscillator signal (LO) and the observed signal by a diplexer, and the splitting of the LO signal by a phase grating. The stability was calculated with the Allan variance and I found that the two elements limiting the stability of our receiver were the 1.4 THz local oscillator and the mixer bias supply. The Martin-Puplett interferometer (MPI) diplexer I designed, built and tested is able to transmit 76 % of the LO power at 2.6 THz and we estimate a transmittance around 79 % for the observed signal. This MPI is operational and ready for the next generation of heterodyne receivers. Splitting the LO signal is essential to build heterodyne receivers with several pixels, which allows us to get spectra of the universe at many positions in the sky simultaneously. I have developed a new kind of grating, called Global gratings, and I made two prototypes of these Global phase gratings able to split the LO beam into four beams. These two phase grating prototypes, a transmissive and a reflective one, were optimized for 610 GHz and showed, respectively, an efficiency of 62 ± 2 % and 76 ± 2 %. These excellent results validate the design and fabrication processes of this new kind of grating. In conclusion, the work accomplished during this PhD constitutes an important step toward the realization of a very stable and highly sensitive 2.6 THz multi-pixel heterodyne receiver using a MPI diplexer., Les observations astronomiques nous permettent d’étudier l’univers et de comprendre les phénomènes qui le gouvernent. La matière visible dans l’univers émet des ondes à des fréquences très diverses, réparties sur tout le spectre électromagnétique (domaines radio, submillimétrique, infrarouge, visible, ultraviolet, X et gamma). Ces ondes nous renseignent sur certaines caractéristiques physico-chimiques des éléments observés (nature, température, mouvement, etc.). Des télescopes couvrant différentes plages de fréquences sont nécessaires pour observer l’ensemble du spectre électromagnétique. Les radio-télescopes, sensibles aux ondes (sub)millimétriques, sont principalement dédiés à l’observation de la matière froide présente dans le milieu interstellaire. Le milieu interstellaire est le berceau des étoiles et son étude est essentielle pour comprendre les différentes étapes de la vie des étoiles. La fréquence maximale d’observation des radio-télescopes est en augmentation depuis la fabrication des premiers radio-télescopes dans les années 1930. Récemment, des radio-télescopes capables de détecter des signaux dans l’infrarouge lointain, au delà de 1 THz, ont été développés. Ces avancées technologiques ont été motivées, entre autres, par la présence, dans le milieu interstellaire, de molécules et d’ions uniquement observables à des fréquences supérieures à 1 THz. Pour observer des raies avec une haute résolution spectrale, les radio-télescopes sont équipés de récepteurs hétérodynes. Ce type de récepteur permet d’abaisser la fréquence de la raie spectrale observée tout en conservant ses caractéristiques (une raie observée à 1 THz peut, par exemple, être décalée à une fréquence de 1 GHz). Cette technique permet d’observer des raies avec une très haute résolution spectrale et c’est pourquoi les récepteurs hétérodynes sont largement utilisés pour les observations de raies spectrales aux fréquences GHz et THz. Dans les récepteurs hétérodynes, un oscillateur local (OL) émet un signal monochromatique à une fréquence très proche de celle du signal observé. Les deux signaux sont superposés à l’aide d’un diplexeur et transmis à un mélangeur. Ce dernier réalise le battement des deux signaux et génère un signal identique au signal observé mais à une fréquence plus faible. Durant ma thèse, j’ai travaillé sur la construction, la caractérisation et l’amélioration d’un récepteur hétérodyne à 2.6 THz. Cette fréquence d’observation (2.6 THz) est l’une des plus hautes atteintes par les récepteurs hétérodynes THz existant actuellement, ce qui constitue un défi technologique très important. Dans le but de caractériser et d’améliorer ce récepteur, je me suis concentré sur trois aspects essentiels .....

Many important astrophysical processes occur at wavelengths that fall within the far-infrared band of the EM spectrum, and over distance scales that require sub-arc second spatial resolution. It is clear that in order to achieve sub-arc second resolution at these relatively long wavelengths (compared to optical/near-IR), which are strongly absorbed by the atmosphere, a space-based far-IR interferometer will be required. We present analysis of the optical system for a proposed spatial-spectral interferometer, discussing the challenges that arise when designing such a system and the simulation techniques employed that aim to resolve these issues. Many of these specific challenges relate to combining the beams from multiple telescopes where the wavelengths involved are relatively short (compared to radio interferometry), meaning that care must be taken with mirror surface quality, where surface form errors not only present potential degradation of the single system beams, but also serve to reduce fringe visibility when multiple telescope beams are combined. Also, the long baselines required for sub-arc second resolution present challenges when considering propagation of the relatively long wavelengths of the signal beam, where beam divergence becomes significant if the beam demagnification of the telescopes is not carefully considered. Furthermore, detection of the extremely weak far-IR signals demands ultra-sensitive detectors and instruments capable of operating at maximum efficiency. Thus, as will be shown, care must be taken when designing each component of such a complex quasioptical system.