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.     

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.     

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.     

High quality electromagnetic oscillations in inhomogeneous coated microsphere

We study transmission of the electromagnetic waves of the near infrared spectral range through the metal-semiconductor spherical stack with a radial dependence of the effective dielectric permittivity of semiconductor layers. Such an inhomogeneity is formed by a high concentration of carriers at the interfaces of thin semiconductor-metal structures and its spatial scale can be of order of a width of narrow metallic layers. Because of complexity of analytical solution, we develop numerical approaches, which allow us to study the features of the electromagnetic wave propagation through such a nonuniform structure. The eigenfrequencies and radial distributions of fields are also discussed.     

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.     

Nonlinear reshaping of terahertz pulses with graphene metamaterials

We study the propagation of electromagnetic waves through a slab of graphene metamaterial composed of the layers of graphene separated by dielectric slabs. Starting from the kinetic expression for two-dimensional electric current in graphene, we derive a novel equation describing the nonlinear propagation of terahertz electromagnetic pulses through the layered graphene-dielectric structure in the presence of losses and non-linearities. We demonstrate strong nonlinearity-induced reshaping of transmitted and reflected terahertz pulses through the interaction with the thin multilayer graphene metamaterial structure.     

Nonlinear pulse propagation in periodic media with and without defects

The influence of single defects within a periodic structure on the nonlinear transmission of optical pulses through the structure is investigated numerically. A stack of alternating linear and cubically nonlinear layers of submicron thicknesses is considered. The simulations are based on a modified equation for the pulse envelope. Diffraction of the pulse has been taken into account, too. The results of simulations have been demonstrated as an essential influence of defects within the periodic structure on the nonlinear propagation of optical pulses, when the carrier frequency is chosen within the stop band of the structure with the defect.     

Superheterodyne Amplification of Sub Millimeter Electromagnetic Waves in an n-GaAs Film

The superheterodyne amplification of sub-millimeter electromagnetic waves in GasAs due to negative differential mobility is analyzed. The nonlinearity arises from the current and the magnetic field of the electromagnetic waves. The case of interaction of two traveling counter propagating electromagnetic waves and the following space charge wave in an n-GaAs film, placed onto i-GaAs substrate, is considered, under a 2D electron gas model. The simulation of this nonlinear interaction shows a certain amplification of the sub-millimeter electromagnetic wave.