Optical constants of silicon nanoparticle thin films grown by laser electrodispersion

The study of films consisting of amorphous close-packed silicon nanoparticles grown by laser electrodispersion is continued. The optical transmission and reflection spectra of films fabricated in vacuum and at various pressures of oxygen introduced into the chamber to passivate the nanoparticle surface are measured. The spectra of the refractive index and extinction coefficient are calculated. The shape of the spectra of the optical constants correlates with that of the spectra of bulk amorphous silicon; however, the values obtained differ from the parameters of bulk amorphous silicon. The differences are caused by the significant volume of voids between nanoparticles and a large number of dangling bonds (defects) on the nanoparticle surface. The optical constants decrease with increasing oxygen content in the films, which is indicative of the passivation of dangling bonds by oxygen.     

Influence of temperature on the mechanism of carrier injection in light-emitting diodes based on InGaN/GaN multiple quantum wells

The experimental current-voltage characteristics and dependences of the external quantum yield on the current density of light-emitting diodes based on InGaN/GaN multiple quantum wells for the wide temperature range T = 10–400 K are presented. It is shown that, at low-temperatures T < 100 K, the injection of holes into the quantum wells occurs from localized acceptor states. The low-temperature injection of electrons into p-GaN occurs due to quasi-ballistic transport in the region of multiple quantum wells. An increase in temperature leads to an increase in the current which is governed by thermally activated hole and electron injection from the allowed bands of GaN.     

sd-Exchange emission in ferromagnetic junctions

The spin-injection emission in a ferromagnetic junction at terahertz frequencies is theoretically analyzed. It is demonstrated that the efficiency of the emission caused by the sd-exchange interaction of the injected spin in which the electromagnetic field is involved strongly depends on the orientation angle of the magnetization of the active region relative to the magnetization direction of the injecting region. The fact that the calculated radiation frequency and power are close to the experimental results shows that the sd-exchange emission must be taken into account in the interpretation of the observed terahertz emission in magnetic junctions.     

Digital demodulation technique for fiber-optic hydrophones based on 3×3 couplers

In this paper,a digitized real-time demodulation system for optical hydrophones based on a 3×3 coupler is proposed.The system is built as a virtual instrument via the dynamic data acquisition platform from NI company.Compared with the commonly used systems composed of analogue circuits,the proposed system has better accuracy and is more flexible in applications.The error analysis of the proposed system is also given.     

卫星地球站天馈系统的技术改造

本文从实际应用出发,以浙江卫星地球站天馈系统为实例,对卫星站上行链路天馈系统的结构和功能作简要分析,剖析目前天馈系统存在的缺陷,并针对问题提出改造思路。结合同期广电总局对全国地球站提出的50dB耦合器的技术改造要求,详细阐述新天馈系统的设计方案和具体实施步骤。     

An Efficient Paging Strategy Based on Paging Agents of Base Stations in Cellular Mobile Networks

We propose a new paging strategy to reduce paging cost by adding paging agents at base stations. When a mobile‐terminated call occurs, the base stations look up the paging agents to determine if terminal paging is actually to be made. An analytical model based on a Markov chain is used to evaluate the performance of the proposed strategy. The numerical results show that the proposed strategy significantly reduces the paging cost compared with the simultaneous paging strategy.     

Narrow vertical beam divergence laser diode based on longitudinal photonic band crystal waveguide

Narrow (<5/spl deg/) vertical beam divergence is realised in an InGaAs-AlGaAs double-quantum well edge-emitting laser diode. A multilayer GaAs-AlGaAs structure was used as a waveguide, acting as a longitudinal photonic band crystal and enabling stable fundamental mode operation. Longitudinal mode grouping effect is observed in the lasing spectrum and attributed to the transverse cavity-induced hole-burning effect.     

Influence of a low-Q shunting medium on the equivalent parameters of a cavity resonator

The influence of the dielectric loss of a low-Q shunting medium on the parameters of the equivalent circuit of a cavity resonator is analyzed. The effect is studied for a radial cavity resonator partially filled with a lossy medium. The influence of field absorption by the shunting medium on the frequency and Q factor of the oscillation excited in the cavity and, consequently, on the parameters of the equivalent oscillatory circuit is studied by means of electrodynamic modeling. It has been found that the loss level changes not only the Q factor but the characteristic impedance of the equivalent circuit.     

Effect of the spectrum of elementary excitations on spinodal decomposition of semiconductor alloys

A new theoretical approach to the determination of the critical temperature of spinodal decomposition of alloys is suggested. The approach is based on the inclusion of the dependences of elementary excitations existing in the system on the alloy composition. It is shown that the most substantial effect on the critical temperature is produced by equilibrium plasma oscillations. An analytical expression for the critical temperature in terms of the band -structure parameters of the alloy is derived. The role of other excitations existing in the system is analyzed. The calculated critical temperatures are correlated with the currently available theoretical and experimental results.     

Representation of electric field strength and potential in the region with circular <Emphasis Type="Italic">n</Emphasis>-connection boundary as a sum of space harmonics

The possibility and reasonability of representing the electric field strength and potential on an open complex plane with n-connected circular boundary and equal lengths of bounding arcs as a sum of space harmonics is shown. Analysis on presence or absence of space harmonics is conducted and their amplitudes are calculated.