Electron spectrum of δ-doped quantum wells by the Thomas-Fermi method at finite temperatures

The electron spectrum of δ-doped quantum wells in n-GaAs is investigated by means of the Thomas-Fermi (TF) method at finite temperatures. This method shows rapid convergence and good accuracy. Under two-dimensional (2D) doping concentrations 10¹³…2×10¹³ cm⁻², the simplest TF method (T=0 K) can be used to calculate the profiles of the potential well up to T≈200 K. The simplest TF method yields correct results for the electron concentrations and the differences of the electron energy sublevels in the quantum well up to room temperature (T∼300 K).     

Comparison of Volume and Integrated P-I-N Modulators in Millimeter Wave Range

Volume and based on surface oriented integrated p-i-n-structures modulators have demonstrated high efficiency in millimeter wave range as quasi-optical modulators and phase shifters. These structures possess high modulation and high-speed properties; sustain great EM powers. However, the modulation characteristics of p-i-n modulators of both mentioned types in millimeter wave range have not been investigated yet. Here, a comparison and criteria of volume and integrated based on Si surface oriented structure modulators in millimeter wave range are presented.     

Parametric amplification of an electromagnetic wave in a waveguide with a ferroelectric

Kiev State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 5, pp. 626–631, May, 1989.     

Modulation instability of the stimulated Brillouin scattering in fibers in a presence of acoustic diffraction

An influence of acoustic wave diffraction on the modulation instability of the backward stimulated Brillouin scattering in fibers is numerically investigated, when a small feedback for the Stokes wave is present. The cases of acoustic waveguide and anti-waveguide fibers are considered. It is shown that a presence of acoustic diffraction may expand the region of occurrence of modulation instability and may lead to 2–5 times increasing the peak amplitude of output Stokes pulses. In this case, a stable train of short powerful Stokes pulses of nanosecond duration is produced at the output.     

Low Noise Quasi-Optic Receiving in Millimeter and Submillimeter Range for Geophysical and Radio Telescope Measurements

This paper is focused on the choice of the module for low noise receiver in millimeter (mm) and sub millimeter (submm) wave ranges used in geophysical remote sensing systems for measurement of geophysical parameters by means of radiobrightness temperatures (radiometer systems obtaining data by means of radiobrightness temperatures). The observed data analysis, used in order to obtain recommendations and forecasts based on the radio telescope measurements and geophysical phenomena in the events of earthquakes, volcano explosions and typhoons, are realized by means of specialized computer codes.     

Pyridyl-substituted [1,3]Dithiolo-[4,5-<Emphasis Type="Italic">b</Emphasis>][1,4]dithiine-2-thiones

We have obtained 5-(2-pyridyl)[1,3]dithiolo[4,5-b][1,4]dithiine-2-thione for the first time by cycloaddition of 2-ethynylpyridine to 4,5-dihydro-1,3-dithioltrithione (isotrithionedithiol). We have studied this thione, 5-(2-pyridyl)- and 5-(4-pyridyl)-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine-2-thiones by mass spectroscopy and also IR, UV, ¹H and ¹³C NMR spectra. We have determined the crystal and molecular structure of 5-(2-pyridyl)-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine-2-thione.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 429–434, March, 2005.     

A Silicon Plasma-Based Wideband Modulator

Theoretical and experimental analysis has been performed for surface oriented silicon plasma-based p,i,n structures used to control high power level, broadband devices. It is shown that these structures are very promising for their use as modulators in the millimeter and submillimeter wave range.     

Quasi-Optical Sensors for Investigation of Acousto-Electromagnetic Phenomena of Popocatepetl Volcano

This article focuses on meteorological electronics based on the space research of acoustic-electromagnetic phenomena caused by Popocatepetl volcano (Mexico). The main purpose is to present two different types of quasi-optical sensors, one of them is formed by a modulator based on a surface oriented p,i,n structure with deep junctions; and by a silicon detector (avalanche photodiode with separated regions of absorption and multiplication: APDSAM). This system guarantee both good sensibility and wide range of sensing, sub-millimeter and millimeter range. This sensor has the advantage that can be realized as a planar array. On the other hand, for the remote measurement of basic meteorological parameters and chemical state by means of radiobrightness temperatures (radiometer systems) a low noise receiver on the base of dielectric waveguide and Schottky diodes cooled by means of cryoelectronic element is used.     

Terahertz P-I-N Modulator

Theoretical and experimental research of silicon surface oriented integrated p-i-n-structures as quasi-optical modulators of terahertz frequency range have been done. The problem of double injection into i-region has been numerically solved. A possible role of nonlinearity in boundary conditions at injecting junctions is pointed out. Our simulations demonstrate that an effective modulation of terahertz wave beams by Si p-i-n-structures can be achieved up till the frequencies 2-2.5 THz. Measurements at 400 GHz confirm the results of simulations. The possibility of modulation of picosecond monopulses is also investigated. The investigation of modulator includes the analysis of the nonlinear losses, which are very important in sub millimeter waves. The field value of the nonlinear effects domination is obtained.     

Parametric Instabilities of Two Kind of Millimeter Waves and Multiplication of Frequency in GaAs Semiconductors

This paper deals, at first, with the non-linear parametric effects on both space charge and electromagnetic waves in GaAs semiconductors. If an external electric field is applied, at the critical field value, the mobility changes its sign and becomes negative, as a result, non-linear instabilities of the interactions are obtained. At the optimal value of electric field, E _opt, all non-linear processes are very effectives. The second point is the multiplication of the wave frequency, which is also effective thanks to the non-linearity. This process is used for carring waves into millimeter range instead of generation process, which in this range is non-effective. The Multiplication effect is based on the using space charge waves.