A W-band (75–110-GHz) phase shifter was designed and numerically modeled. The phase shifter is a periodic array of rectangular patch antennas on a dielectric substrate with built-in PIN diodes. It was numerically demonstrated that one can achieve a phase shift of the transmitted wave up to 87° at a frequency of 96 GHz with transmittance losses of no more than –7 dB.

We studied the absorption of microwave electromagnetic radiation incident normal to a two-dimensional electron system on a dielectric substrate with a metallic back reflector. We have shown that the presence of a back gate strongly modifies the spectrum of plasmon polaritons in such a structure. We observe a transverse plasmon mode which starts from zero frequency at zero magnetic field and follows renormalized cyclotron resonance. This renormalization occurs from the hybridization of plasma modes with Fabry-P & eacute;rot photonic resonances in the substrate, which indicates their transverse nature. Finally, we speculate that the observed modes resemble helicon waves in three-dimensional metals.

Resonant microwave absorption by two-dimensional electron systems based on GaAs/AlGaAs heterostructures with a metallic back gate is investigated. The regime where the velocity of a screened plasma wave in a two-dimensional system calculated in the quasi-static approximation exceeds the speed of light in the substrate is obtained. It is established that relativistic retardation-related effects in this situation lead to significant changes in the dispersion and magnetic-field behavior of screened two-dimensional plasmons. It is found that the retardation effects result in the pronounced renormalization of the cyclotron and plasma frequencies. There is good agreement between the experimental results and the existing theory.

The latest achievements in the study of the physical properties of plasmon excitations in partially screened two-dimensional electron systems based on AlGaAs/GaAs heterostructures have been reviewed. It has been revealed that a proximity plasmon, i.e., a specific type of two-dimensional plasma waves, is excited in such systems. It has been established experimentally that these plasma waves have a number of new physical properties. First, the dispersion relation of partially screened plasmons combines features of both screened and unscreened two-dimensional plasmons. Second, an edge branch is absent in the magnetic dispersion relation of the revealed proximity mode. Finally, a "charged" relativistic plasma mode with a number of unique properties is excited in the system if the gate is connected to the two-dimensional system through an external circuit. The reported new results expand the horizon of possible applications of plasmonics in the field of microwave and terahertz electronics.

Phase waveplates for THz beam shaping were developed, calculated, and implemented. Developed phase plates could be 3D-printed from commercially available polymers, which makes them affordable and fully customized. These waveplates allow to widely and easily manipulate THz beam shape.

We have investigated plasma excitations in a disk-shaped two-dimensional electron system (2DES), the edge of which was covered by an overlaying metallic gate. We have found that the microwave response of the structure is dominated by the proximity plasma mode propagating along the disk edge. Significantly, we find that as the overlap between the 2DES and the gate tends to zero, the frequency of the proximity plasmon makes a transition to that of an ordinary 2D plasmon in the ungated area of the 2DES. We also observe that tuning the electron density under the gate results in a crossover from the proximity to the laterally screened 2D plasmon. The experimental findings are analyzed using the plasmonic lumped-element approach.

An investigation is performed of the relaxation of plasma excitations in two-dimensional electron systems (2D-ESes) in GaAs/AlGaAs heterostructures. The effect radiational and incoherent collisional relaxation mechanisms have on the linewidth of cyclotron magnetoplasma resonance (CR) is studied. CR arises as a pure resonance that does not hybridize with dimensional magnetoplasma excitations. It is shown how magnetoplasma resonances form a CR’s fine structure due to the interaction between coherent radiative and incoherent collisional mechanisms of two-dimensional plasma relaxation. A comparative analysis is performed of the dependences of cyclotron and transport periods of relaxation on both the temperature and electron density of 2D-ESes. It is demonstrated that the period of cyclotron relaxation could exceed that of transport at low electron densities.

We have investigated the spectrum of two-dimensional (2D) plasmon polaritons over the full range of magnetic fields. In our study, we investigate a disk-shaped two-dimensional electron system (2DES) with a metallic gate on the backside of the substrate. Importantly, we show that 2D plasmon polaritons hybridize with the TM$_0$ photonic mode of a dielectric waveguide formed by a sample substrate. We have developed a theory for plasmon-polaritons in an infinite 2DES. We find the experimental data to be in good agreement with the developed theory.

We investigate the electrodynamics of a disk-shaped two-dimensional electron system in the proximity of a screening gate. The two-dimensional plasmons in the system under study exhibit the linear dispersion characteristic of acoustic plasma waves. We experimentally achieve the limit when the velocity of acoustic waves approaches the speed of light. We show that retardation effects lead to strong coupling between acoustic plasmons and the light, which is manifested in the renormalization of the electron effective mass. We develop a theory to substantiate the observed phenomena.

В данной работе экспериментально исследуются плазменные возбуждения в высококачественной двумерной электронной системе (ДЭС) на основе AlAs [1]. Образец представлял собой шесть эквидистантных дисков ДЭС, расположенных в щелях копланарного волновода. Исследования проводились при помощи методики резонансного поглощения микроволнового излучения. Микроволновая магнитоспектроскопия является наиболее прямым способом характеризации поверхности Ферми и определения эффективных масс. В микроволновом отклике дисков двумерных электронов были обнаружены две магнитоплазменные моды: краевая и циклотронная. Удивительной особенностью обнаруженных плазменных мод является щель по частоте между ними в нулевом магнитном поле (рис. 1). Это является следствием сильной анизотропии масс носителей заряда в AlAs квантовых ямах. Из частот плазменных возбуждений в нулевом магнитном поле были получены значения эффективных масс вдоль основных кристаллографических направлений m1=(1.10±0.05)m0 и m2 = (0.20±0.01)m0. Полученные результаты соответствуют случаю однодолинной сильно анизотропной поверхности Ферми, так как остаточная внутриплоскостная деформация снимает вырождение по энергии долин. Было установлено, что повышение электронной плотности приводит к качественным изменениям в спектре плазмы, что указывает на заполнение второй долины. Напрямую были определены электронные плотности в каждой из долин и разность энергий между ними из отношения плазменных частот. Литература [1] Muravev V. M., Khisameeva A. R., Belyanin V. N., Kukushkin I. V., Tiemann L., Reichl C., Dietsche W., and Wegscheider W., Phys. Rev. B 92, 041303(R) (2015) [2] Shayegan M., De Poortere E.P., Gunawan O., Shkolnikov Y.P., Tutue E., Vakili K., Phys.stat.sol.(b) 243, No. 14, 3629-3642 (2006) [3] De Poortere E.P., Shkolnikov Y.P., Tutuc E., Papadakis S.J., Shayegan M., Applied Physics Letters,Vol. 80, No. 9 (2002) Рис. 1. Магнитодисперсия плазменных

We have studied the microwave response of a high-mobility two-dimensional electron system (2DES) contacted by two side electrodes. Using kinetic inductance of the 2DES and inter-electrode capacitance, we have constructed a subwavelength 2D plasmonic resonator. We have shown that the resonant frequency of this circuit can be controlled by 2D electron density, external magnetic field, or size of the electrodes. This opens up possibilities for using arrays of plasmonic circuits as tunable components in different frequency ranges.

Aim. Demonstration of potentials of preoperative planning and implementation of surgical resection in patients with adrenal cysts. A clinical observation of a successful surgical treatment of a rare pathology cyst of the right adrenal is presented. The choice of surgical treatment tactics is determined by the size of tumor and clinical presentation of the disease. The surgical treatment was accomplished laparoscopically which permitted to reduce the time of recovery and rehabilitation of the patient. In this clinical observation, the benefit of using 3D-modeling of the surgical area was shown for visualization of topographic and anatomic peculiarities and facilitation of the intraoperative navigation with the help of Avtoplan program developed by Samara State Medical University. Conclusion. Preoperative 3D-modeling permits to prepare to surgical intervention taking into account individual anatomic peculiarities of a patient, and to determine the optimal volume of the operation.

A new electromagnetic plasma mode has been discovered in the hybrid system formed by a highly conductive gate strip placed in proximity to the two-dimensional electron system. The new plasmon mode propagates along the gate strip with no potential nodes present in transverse direction. Its unique spectrum combines characteristic features of both gated and ungated 2D plasmons. The new plasma excitation has been found to exhibit anomalously strong interaction with light.

An electromagnetic plasma mode has been discovered in the hybrid system formed by a highly conductive gate strip placed in proximity to the two-dimensional electron system. The plasmon mode propagates along the gate strip with no potential nodes present in transverse direction. Its spectrum combines characteristic features of both gated and ungated two-dimensional plasmons. The plasma excitation has been found to exhibit anomalously strong interaction with light.

Plasma excitations with different symmetries in a single two-dimensional electron disk are studied by optical detection of resonant microwave absorption. The manifestation of retardation effects for “dark” axisymmetric plasma excitations is studied for the first time. It is shown that the hybridization of these excitations with light is much smaller than the hybridization of dipole active two-dimensional plasmons. An unusual crossing of the magnetic field dispersion of “bright” and dark plasmon-polariton modes is observed in a perpendicular magnetic field.

Terahertz radiation has great potential for security applications due to its penetrating ability combined with harmlessness for living organisms. Here we report about development of the terahertz security system for the remote detection of hidden objects. The system works in the reflection mode and includes $\mathbf{32\times 32}$ pixel imaging camera, objective lens, and several (six or more) 100 GHz IMPATT diode sources.