Polarization properties of enhanced self-diffraction in sillenite crystals

Doppler-enhanced self-diffraction in two-beam coupling experiments with sillenite crystals exhibits pronounced optical polarization effects due to the concomitant presence of natural optical activity and electric-field-induced linear birefringence. Coupled wave equations that describe the polarization properties, exclusive of self-diffraction effects, have previously been derived for the two principal crystal orientations most commonly used in photorefractive recording. In this paper, the coupled wave equations are combined with a linearized model of the photorefractive recording process (single trap level, single mobile charge species) to analyze the impact of self-diffraction effects on the polarization state evolution. Numerical solutions of these equations yield optimum configurations for enhanced gain and improved image contrast in two-wave mixing with such materials. In addition, inclusion of optical activity in the model emphasizes the contribution of this effect to the apparent reduction of the effective electrooptic coefficient of bismuth silicon oxide crystals.     

冷等离子体对硅粉薄层纯化的动力学分析

利用提高硅粉薄层温度的方法，使冷等离子体对硅提纯达４Ｎ（９９．９９％）。本文用反应动力学的方法分析提纯机理，建立必要的方程以探讨影响提纯的因素。     

Heat transfer in forced convection through fins

A novel structure for cooling silicon chips involving passage of water through fins etched in the back of the chips has recently been described in the literature. The properties of silicon and the nature of the structure are such that approximations that allow an analytic solution to the heat transfer problem in the structure can be introduced. Formulas for the fin and channel dimensions that provide optimum cooling under various conditions can then be derived. The results are also presented in graphical form and by means of examples.     

Optimal power-flow solutions for power system planning

Since the development of sparsity techniques by Tinney, the power-flow program has become an extremely effective and often used tool for planning electric power networks. This program solves for the unknowns--voltages, phase angles, etc.--of a set of simultaneous nonlinear algebraic equations, the ac power-flow equations. The optimum power flow is likely to replace, in due time, the normal power flow in many important planning functions discussed in this paper. A number of mathematical programming techniques have recently been studied to solve the optimum power flow and several small-to-medium sized experimental programs have been written. The generalized reduced gradient (GRG), one of the most elegant nonlinear-programming techniques, is described and it is shown how it can be extended to solve optimum power flows of very high dimension (of the order of several thousand nodes). This extension consists mainly of using sparsity techniques in several of the solution steps of the GRG.     

Minimum entropy quantizers and permutation codes

Amplitude quantization and permutation encoding are two approaches to efficient digitization of analog data. It has been proven that they are equivalent in the sense that their optimum rate versus distortion performances are identical. Reviews of the aforementioned results and of work performed in the interim by several investigators are presented. Equations which must be satisfied by the thresholds of the minimum entropy quantizer that achieves a prescribed meanrth power distortion are derived, and an iterative procedure for solving them is developed. It is shown that these equations often have many families of solutions. In the case of the Laplacian distribution, for which we had previously shown that quantizers with uniformly spaced thresholds satisfy the equations whenr=2, other families of solutions with nonuniform spacing are exhibited. What had appeared to be a discrepancy between the performances of optimum permutation codes and minimum entropy quantizers is resolved by the resulting optimum quantizers, which span all entropy rates from zero to infinity.     

High-power pulsed beam-lead IMPATT diodes for millimetre waves

IMPATT diodes with technologically integrated beam-leads were fabricated. Since no diode bonding is required, a total diode thickness of less than 2 ?m can be realised reproducibly. With optimum device packages, peak pulse output powers of more than 10 W at 70 GHz have been achieved from silicon single-drift IMPATT diodes.     

Parametric studies and optimization of the beta-voltaic cell—II open-circuit voltage and power efficiencies

Theoretical analyses on the silicon beta-violtaic cell have shown that contrary to the short-circuit current the open-circuit voltage is more sensitive to junction parameters than to bulk parameters. Optimum maximum power is obtained by a compromise between high current and high voltage. The resistivity of the silicon substrate under the optimum power condition is found to be about 0·3 Ω . cm. Optimization of overall efficiency involves maximizing the effectivness of the junction diode to collect generated carriers and minimizing the self-absorption in the active source layer; a layer of radioactive Pm₂O₃ with 1·0–1·5 Ci/cm² appears to be optimum. The corresponding overall power efficiency is 2·5 per cent for a cell irradiated from the front side. Higher efficiency is possible when beta particles are injected from both the front and the back of the silicon slice; under these conditions there is an optimum substrate thickness whcih is about 125 μm for maximum efficiency.     

Numerical Simulation of Spectral Response for 650 nm Silicon Photodetector

The theoretical spectral response formula of the N+-N-I-P+ silicon photodetector with high/low emission junction is given. At the same time, considering the process requirements, the optimum structure parameters of silicon photodetector are obtained by numerical calculation and simulation. Under the condition of these optimum structure parameters, the responsivity of the silicon photodetector will be 0.48 A/W at 650 nm.     

Hydrodynamic equations for semiconductors with nonparabolic bandstructure

A system of generalized hydrodynamic equations is derived from Boltzmann's transport equation for semiconductors without the assumption of a parabolic band structure. After some simplifications these equations can be arranged in such a way that their structure is similar to that of the well-known conventional ones. For this purpose the quantity carrier temperature is redefined and five relaxation times have to be introduced instead of the two in use so far, in order to take nonparabolicity into account. For all quantities of interest results from Monte Carlo simulation are presented for silicon with an impurity concentration of up to 10¹⁸ cm^-3 and an electric field of up to 200 kV/cm. They show that two of the five relaxation times are not distinguishable; hence, for silicon at room temperature the number of relaxation times can be reduced to four. Considerable deviations from results derived under the assumption of a parabolic band structure demonstrate the necessity of this generalized hydrodynamic model. The new hydrodynamic model is applied to a n-channel LDD MOSFET with a 0.5-μm channel length. The results agree well with the results of Monte Carlo device simulation     

Numerical Simulation of Spectral Response for 650 nm Silcon Photodetector

The theoretical Spectral response formula of the N^ -N-I-P^ silicon photodetector with high/low emission junction is given.At the same time,considering the process requirements,the optimun structure parameters of silicon photodetector are obtained by numerical calculation and simulation.Under the condition of these optimum structure parameters,the responsivity of the silicon photodetector will be 0.48A/W at 650 nm.