具有非对称高斯反射率相位共轭光腔的基模

由高斯光束泵浦的四波混频相位共轭反射镜(PCM)具有横向高斯分布的反射率.这种分布是空间非对称的.本文给出这种PCM(包括自泵浦情况)的光束变换矩阵,把它用于自泵浦相位共轭光腔的分析;得出腔内振荡是椭圆高斯光束的结论.     

相位共轭光腔的基本物理性质

用一面由四波混频非线性相互作用产生的相位共轭镜(PCM)和另一面真镜(RM)组成的相位共轭光腔(PCR),将会得到十分优良的性质。 为了描写PCM的运转特性,Yariv等和Siegman等定义了该元件光线变换矩阵的第一形式(M_(PCMI));并已由此得出PCR若干有用的性质。但,M_(PCMI)并没有包含相位共轭运算,ABCD定律不再适用,需要人为地加置共轭,给腔模的分析带来很大的困难。 本文定义了PCM变换矩阵的第二形式(M_(PCMH))。所有的变换(包括共轭运算)均包含在M_(PCMH)的矩阵元中,普通的ABCD定律仍然适用,从而非常简洁地导出了PCR的基模。进一步运用M_(PCMH),得到了基模的微扰稳定性、高价模和非简并模。     

相位共轭镜变换矩阵及相位共轭光腔

本文提出了能更确切地描述相位共轭镜运转特性及揭示相位共轭镜工作本质的变换矩阵。将新矩阵用于研究相应的相位共轭光腔，分别讨论了从RM和PCM端输出的简并模和非简并模。     

双相位共轭光腔的横模及其特性

人们对相位共轭光腔(PCR)的研究开始集中于单PCR,即由一块相位共轭镜(PCM)和一块真镜(RM)组成的光腔。对单PCR的横模、纵模已有比较深入的讨论。最近,双PCR即中由两块PCM组成的谐振腔已受到人们的重视。本文运用PCM的第Ⅰ和第Ⅱ变换矩阵分别计算了双PCR的简并模、非简并模,两种方法得出相同的结果。结果表明,双PCR具有与常规球面镜腔及单PCR不同的物理特性。进一步着重分析了双PCR的热稳定性和微扰稳定性,并讨论了非简并模过渡到简并模时的跃变。     

相位共轭腔的新问题

本文指出在相位共轭腔中存在如下两个新问题:(1)在由球面镜与相位共轭镜构成的谐振腔中,球面波和高斯光束均是腔的本征模;(2)在由高斯反射率镜与相位共轭镜构成的谐振腔中,球面波和高斯光束均不自洽.     

相位共轭镜和相位共轭腔

本文使用矩阵光学方法,分析了下述论题:1.相位共轭镜的两类变换矩阵及其物理意义;2.相位共轭腔与常规稳定腔的比较;3.相位共轭腔的模参数;4.有频移的相位共轭腔;5.相位共轭腔的稳定性,并提出了一些问题加以讨论。     

带SBS相位共轭镜的高重复频率高功率激光系统研究进展

受激布里渊散射(SBS)是一种三阶非线性光学效应,SBS相位共轭镜(PCM)是基于SBS的自抽运PCM,能实时补偿放大器和放大光路中的波前畸变,改善激光器的输出光束质量,其应用越来越广泛。简要介绍了SBS-PCM激光系统的基本原理和典型装置,并概述了国内外液体和固体SBS相位共轭技术在高重复频率高功率激光系统中的研究进展,提出带SBS-PCM的高重复频率高功率激光系统有待解决的问题。     

拉盖尔-高斯光束通过含矩形光阑光学系统的变换

基于厄米-高斯模与拉盖尔-高斯模的变换关系和递推算法,推导出拉盖尔-高斯（LG）光束通过含矩形光阑近轴ABCD光学系统传输的递推公式。作为应用例,对LG光束通过光阑透镜分离系统的变换作了数值计算和分析。本文有关结果提供了一个研究有不同几何对称性光束间变换的有效方法。     

弱高斯光阑近似和相位共轭腔

本文证明了在弱高斯光阑近似下,相位共轭腔中不存在确定模,只有当非弱高斯光阑处于腔中或相位共轭镜之前,相位共轭腔才具有确定的模。     

应用于动态核极化核磁共振系统的改进型传输线研究（英文）

基于几何光学理论和矢量衍射理论,设计了263 GHz DNP-NMR谱仪的改进反射镜系统,并进行了数值模拟.该系统包括两个波纹波导、一个抛物面镜和一个角度可调的相位校正镜.仿真结果表明,获得了聚焦良好的类高斯输出光束,其标量高斯模含量为99.90%,矢量高斯模含量为99.55%.只有通过调整相位校正镜的角度来匹配DNP-NMR样品,才能改变输出光束的方向.当输出光束方向在±15°变化时,标量高斯模含量约为99.57%,矢量高斯模含量约为98.97%.     

变换矩阵的两类分解方式和等效性问题

详细讨论了由Gasperson_(1)和Arsenaulf_(2)分别提出的变换矩阵M分解的一些问题。证明:(1)文献〔幻中光学系统的焦面表示法与 C\ 0时 CasPeroon的一种矩阵分解法等效,(2)对 PCM,可通过引人它的等效变换矩阵M_(PCM,II)来进行矩阵分解。     

Sensitivity of phase-conjugate resonators to intracavity phase perturbations

The sensitivity of phase-conjugate resonators to phase perturbations is analyzed numerically. It is shown that as long as the phase-conjugate mirror (PCM) intercepts most of the light traveling towards it, this type of resonator provides much improvement over conventional optical cavities.     

Semiconductor laser dynamics for feedback from afinite-penetration-depth phase-conjugate mirror

Most of the previous treatments of semiconductor lasers subject to optical feedback from a phase-conjugate mirror (PCM) have assumed that the PCM responds instantaneously. Furthermore, the mechanism responsible for phase conjugation does not usually enter into the analysis. In this paper, we derive the time-dependent reflectivity of a PCM created through nondegenerate four-wave mixing in a Kerr-type nonlinear medium. The resulting laser dynamics are compared with the case of the ideal PCM, as a function of the external-cavity length, the PCM reflectivity, and the PCM interaction depth. The PCM with a significant interaction depth tends to suppress otherwise chaotic output and produces pulses whose repetition rate is tunable by varying PCM reflectivity. At high feedback levels, it stabilizes the laser output. We use the circle-map formalism to explain our numerical results     

Mean field theory of optical bistability in a phase-conjugate resonator using nearly degenerate four-wave mixing

A mean field theory of nearly-degenerate four-wave mixing is developed for the optical bistability, which has recently been found in a phase-conjugate resonator consisting of a normal mirror and a phase-conjugate mirror under relatively strong pumping. The bistability in transmission of the probe beam occurs as the mirror separation or the probe offset frequency is changed, but for a limited range of probe beam intensity. This behavior is explained as occurring under injection-locked conditions because of combined effects of tilting and broadening, or narrowing of the resonance curves due to nonlinearities in the phase-conjugate reflectivity arising from pump depletion.     

Optical phase conjugation of multiwavelength signals in adispersion-shifted fiber

Optical phase conjugation (OPC) of multiwavelength signals in a dispersion-shifted fiber (DSF), which can be used for dispersion compensation in the wavelength division multiplexing communication system, is theoretically studied. The multiwavelength phase-conjugate signals are generated by four-wave mixing (FWM) in the dispersion-shifted fiber. There are the pulse-shape distortion and the induced frequency chirping in the phase-conjugate signals owing to pump depletion and the cross-phase modulation among the signals and phase-conjugate signals, respectively. The FWM among the pump wave, signals, and phase-conjugate signals causes unequal conversion efficiencies for the multiwavelength signals and enhances the induced frequency chirping in the phase-conjugate signals. The induced frequency chirping may deteriorate the restoration of the pulse shape. Both the pulse-shape distortion and induced frequency chirping increase with the signal and pump powers. The formula for the induced frequency chirping that is only caused by the signals through cross-phase modulation is derived. The requirement of the signal power in the dispersion-shifted fiber for the restoration of the pulse shape by the optical phase conjugation is estimated and numerically verified     

Investigation of 9.6 kb/s data transmission via a pcm link at 64 kb/s with and without link errors

The problem of pulse code modulation (PCM) bit errors causing voice frequency (VF) modem errors has been studied in detail. The error mechanism consists of the addition of an impulse response type error signal added to the reconstructed VF data signal waveform at the digital-to-analogue (D/A) output of the PCM decoder. This error signal may cause a burst of errors registering in the VF modem receiver, depending on which PCM bit is in error. Numerous data have been collected in a laboratory experiment and analysed in various ways. The average bit error rate (BER) enhancement factor of VF data over PCM is between 10 and 20. For each PCM bit in error, an average of two VF data bits are in error. The analysis leads to suggestions for possible solutions to the problem.     

利用两波耦合增强BaTiO_3晶体的自泵浦位相共轭反射

本文报道了利用BaTiO_3晶体的两波耦合和自泵浦效应,实现高位相共轭反射率的方法。给出位相共轭反射率R随两耦合光束之间的夹角2θ,以及光束强度比β变化的实验结果。在适当的条件下(2θ≈35°,β=2600),得到共轭反射率大于35。     

基于simulink的脉冲编码调制系统设计

脉冲编码调制(PCM)是一种将模拟语音信号变换成数字信号的编码方式,已用于市话中继传输和大容量干线传输以及数字程控交换机,并在用户话机中采用.本文建立了基于Simulink的PCM仿真系统,将声音信号、均匀量化的PCM信号、A律非均匀量化的PCM信号、μ律非均匀量化的PCM信号进行了比较,对PCM系统的分析设计具有重要的意义.     

A mixed-mode PWM controller

In this article, a mixed-mode (MM) PWM controller for dc–dc power converter topologies is presented and analysed. Compared to the conventional peak current-mode (PCM) controller, the proposed controller exhibits better results in terms of robustness towards load and reference voltage variations while maintaining better dynamic response. In the PCM controller, the control signal is a combination of inductor or, most often, switch current and a suitable compensation ramp which in the most common applications is constant. In the proposed controller, the constant compensation ramp has been replaced by a ramp voltage which is proportional to the output voltage taking into consideration the output voltage variations during load and reference transients. Consequently, the proposed controller, which exhibits the same advantages as with the PCM controller, additionally exhibits better load and reference performance for constant output voltage and output tracking applications without increasing the cost and the complexity of the control circuit. Finally, in order to verify the theoretical analysis and conclusions, both control schemes (i.e. PCM and MM) have been simulated and experimentally tested using a 75 W buck converter unit.