高功率激光驱动器中小尺度自聚焦和噪声模型

 建立了一套线性的近似分析方法，研究高功率激光驱动器中强激光传输的小尺度自聚焦效应和相位噪声对光束传输和光束质量的影响，给出了系统噪声强度、B积分值与光束近场调制对比度之间的定量关系。研究表明,为保证输出光束质量，即近场调制对比度小于给定值，系统内的噪声强度必须符合一定的谱分布。     

Mode beating in spot-size converter lasers

An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper.     

Analysis of reflectance and modulation spectroscopic lineshapes in optoelectronic device structures

We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures.     

射束有效宽度与成像系统MTF关系的研究

射线成像系统的射线有效宽度是评定系统成像分辨率的重要成像指标。以试验的方法,通过测试系统成像的MTF,通过对成像分辨率与射线有效宽度的关系进行研究,为射线数字成像(DR)及工业CT系统设计提供了参考。     

Numerical reconstruction of an infrared wavefront utilizing an optical phase modulation device

We utilize nitroanisole, that absorbs infrared (IR) radiation as heat, as an optical modulation device based on a thermal process. The nitroanisole exhibits a thermal lens effect, i.e. a temperature dependent refractive index. Hence, the nitroanisole can induce phase modulation to visible light, in direct response to intensity of the incident IR radiation. The proposed method can be used to obtain the phase modulation distribution that corresponds to the IR intensity distribution, i.e. the IR hologram itself, on the nitroanisole by examining the phase map of visible light that is modulated upon passing through the nitroanisole. The IR wavefront can be reconstructed by calculating extracted IR holograms through the Fresnel transform. It is verified that both the amplitude and the phase of the IR wavefront can be reconstructed accurately by proposed method.     

386微机稳压电源的电路分析及改进

ＭＰＵ－２００Ｐ型３８６微机电源是典型的半桥式脉宽调制型开关稳压电源。本文对它的工作原理进行了分析，并提出一种改进的方法。     

用激活性非线性介质Nd：MgO：LiNbO3产生二次谐波

以Nd:MgO:LiNbO_3同时兼作激活介质和非线性光学材料,研究自倍频激光器。用小型氙灯泵浦,在室温下获得二次谐波激光(0.547μm) 阈值小于4.8'J,最大输出400μJ/shot,工作温度范围大于20℃～45℃,无光损伤。     

信号、噪声通过线性工作系统设备过程中信噪比的变化

本文就信号、噪声通过线性工作系统设备过程中信噪比变化的问题，提出一个简单和实用的模型，建立相应的计算公式，并在视频领域和音频领域对公式展开讨论，进一步阐述公式的实用性，可作为工作系统的设计和调整的参考，以祈获得更好的社会效益和经济效益．     

Study of hot bands in the B2Σ+u-X2Σ+g system of C-2 anion

Optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy was employed to observe the visible absorption spectra of the B^2Σ^+_u-X^2Σ^+_g electronic transition of C^-_2. Four hot bands (0,1), (1,2), (2,3) and (3,4) have been observed and the band (3,4) is measured directly for the first time, so far as we know, by absorption. A rotational analysis was carried out to obtain molecular constants. With the Franck－Condon principle and the vibrational Boltzmann distribution, we have estimated the vibrational temperature of C^-_2 to be about 3000K.     

一种新型的数字编码轨道电路

基于现有UM71无绝缘轨道电路的传输通道,讨论了各种传输方案,提出了一种采用模拟调频方式的32位数字编码轨道电路,选用TMS320C32作为CPU,设计了发送和接收子系统,最后给出了室内仿真试验及其结果.