原子光学讲座第一讲几何与波动原子光学及其器件

文章首先简单介绍了冷原子操纵与控制的基本原理。然后，重点介绍了几何与波动原子光学及其器件的研究内容、潜在应用和最新进展，其中包括：原子束的反射和原子反射镜；原子束偏转（折射）、聚焦成像和原子透镜；原子衍射和原子光栅；原子干涉和原子干涉仪；原子全息学及其技术等。     

《发光学报》征稿内容

本刊征集凝聚态物质中和激发态过程研究有关的原创性论文。主要学术专题包括：1．无机、有机和生物材料的光致发光、电致发光和阴极射线发光及其应用；2．量子阱材料、光子晶体材料、左手材料、纳米材料的光学和光电性质及其应用；     

国内声学文献分类索引

（声学分类：43.10总类；43．15标准；43．20一般线性声学；43.25非线性声学；强声学；43.28航空声学；大气声学；43.30水声学；43.35超声学，量子声学及声的物理效应；43．40机械振动和冲击；43.45统计声学；43.50噪声：影响和控制；43.55建筑声学；43.60声信号处理，声全息技术；43.63生理声学；43．66心理声学；43．70语言通信；43．75音乐与乐器；43.30生物声学；43.85声学测量与仪器；43．88换能器；声音的产生与复制设备）43．10总类射线探伤中的缺陷模型及其检出灵敏度李衍无损检测，1996,18(9)：249射线探伤中的缺陷模型及其检出灵…     

1995年第6期《物理》内容预告

１９９５年第６期《物理》内容预告知识和进展扫描隧道显微镜的最新进展与原子搬迁（白春礼）；闪光二号──一台太瓦级脉冲电子束加速器及其应用（邱爱慈等）；光学悬浮及其应用（赵理曾等）；新型原子滤光器（孙献平等）；液晶小体系物理和ＰＤＬＣ显示材料（杨玉良等）...     

莱特兄弟发明飞机成功的创造学启示

分析了莱特兄弟发明飞机成功的历史经验及其创造学启示:正确选题；重视学习和继承前人的研究成果；抓住主要矛盾并确定正确的主攻方向；注重理论的指导作用；强调试验和实验的重要性；具体问题具体分析并寻找解决问题的可能途径；抓住新技术诞生的历史机遇.     

遗传密码是怎样破译的

文章具体介绍了遗传密码破译的过程：三联体密码的提出；克里克对遗传密码性质的阐述和实验证明；尼伦伯格关于同聚核苷酸对应的氨基酸的发现；奥乔亚关于异聚核苷酸对应的氨基酸的发现；科拉纳关于密码子系列次序的确定；全部密码子的破译及其特征．     

铝的光度分析简介

介绍了光度法分析铝的一些方法；讨论了显色时干扰物质及其消除；比较了测定铝的显色剂。     

型芯、模具及其制造和注射成型工艺(Ⅰ)

基于我国光学塑料元件成型技术落后于技术发达国家的情况，同时考虑到塑料非球面透镜又是我国目前注射成型的难关，并可望在型芯、模具及其制造和注射成型工艺上有所突破，而塑料非球面透镜又主要采用的是模具及注射工艺，所以本刊编辑部将从１９９８年第４期开始不定期的报道国外塑料模具型芯、模具及其制造、注射成型工艺等方面的有关信息，以此能对我国从事光学塑料元件制造的工程技术人员有所帮助。不定期报道的主要内容有：塑料模具设计要点；模具涂层；流态分析；模具制造的改进；注射成型；注射成型机；成型工艺参数；熔流及工艺性；如何减少成型元件的内应力；材料的选择；注射故障的排除等等。     

型芯、模具及其制造和注射成型工艺(Ⅱ)

基于我国光学塑料元件成型技术落后于技术发达国家的情况，同时考虑到塑料非球面透镜又是我国目前注射成型的难关，并可望在型芯、模具及其制造和注射成型工艺上有所突破，而塑料非球面透镜又主要采用的是模具及注射工艺，所以本刊编辑部将从１９９８年第４期开始不定期的报道国外塑料模具型芯、模具及其制造、注射成型工艺等方面的有关信息，以此能对我国从事光学塑料元件制造的工程技术人员有所帮助。不定期报道的主要内容有：塑料模具设计要点；模具涂层；流态分析；模具制造的改进；注射成型；注射成型机；成型工艺参数；熔流及工艺性；如何减少成型元件的内应力；材料的选择；注射故障的排除等等。     

固体材料激光冷却的实验研究及其最新进展

近年来，基于反斯托克斯荧光制冷(Anti—Stokes Fluorescent Cooling)的固体材料激光冷却技术得到了快速发展。本文首先简单介绍了固体材料激光冷却的基本原理及其技术；其次，详细介绍了各种固体激光冷却的新材料、新方案和新结果及其最新实验进展；最后，就固体激光冷却技术的应用前景及其未来发展方向等问题进行了简单讨论与展望。     

部分相干光通过强湍流对通信系统误码率的影响

为研究部分相干光通过强湍流对系统误码率的影响,借助对激光在大气湍流场中的传输方程进行解析求解(忽略系统中其他噪声,仅考虑由大气湍流引起的系统误码率),得到不同湍流内尺度、传输激光波长和光源相干参数条件下,系统误码率和传输距离的关系.结果表明:在强湍流条件下,当发射天线数目达到一定时,随着传输距离的增加,系统误码率逐渐增大,但增大到一定程度后趋于饱和;光源相干参数越大,系统误码率越低;湍流内尺度越大,系统误码率越高;传输激光波长的变化对系统误码率无明显影响.     

卫星振动对星间光码分多址系统性能的影响

卫星振动是影响星间光CDMA通信系统性能的一个重要因素.考虑多用户干扰、背景光噪音、热噪音、接收机噪音和卫星振动,给出了基于PPM信号格式的星间二维光CDMA通信系统的系统模型.采用数值分析的方法,详细分析了卫星振动对该系统误码率性能的影响.结果表明,码速率、通信波长和卫星振动都会影响星间二维光CDMA通信系统的误码率性能.当卫星振动标准偏差σ≤4×10－7时,卫星振动对系统误码率性能的影响较小;当卫星振动标准偏差σ≥1.2×10－6,卫星振动对系统误码率性能的影响很大,得到的误码率难以满足系统的通信要求,需要采用卫星振动抑制或补偿等技术提高星间二维光CDMA通信系统的误码率性能.     

水声通信中低码速率语音编码算法的研究

中远距离(>10 km)水声语音通信时,由于可利用带宽窄、复杂多变等不利因素对信息传输率的制约,语音编码速率应降到尽可能的低。利用水声信道传播时延大的特点,结合人耳听觉感知的特性,在深入研究混合激励线性预测编码(MELP)标准之后,提出一种语音编码速率可调节的变比特率语音编码算法。其平均码速率约600 bps,主观语音质量评估平均得分(PESQ MOS)约2.8分。对该编码算法性能进行了计算机仿真和海上实验验证。实验及仿真表明,在误码率不高于10-3时,本算法表现良好且稳定,合成语音清晰可懂,易于辨认说话人。      

Large Signal Analysis of FM-AM Conversion in Dispersive Optical Fibers for PCM Systems Including Second Order Dispersion

By using large signal analysis for dispersive optical fiber, the FM-AM conversion with respect to binary intensity modulated PCM systems including second order dispersion term is discussed. The modified expression for power penalty has been derived and its impact on laser linewidth and bit rate has been investigated. For power penalty less than 0.5 dB, the plots between bit rate and transmission distance are plotted. It is seen that the transmission distance increases with decrease in linewidth over significant bit rates. The transmission distance with first order dispersion term for 300 MHz linewidth is approximately 800km. With proper first order dispersion compensation, i.e., with second order dispersion only, the transmission distance can be enhanced to 10 8 km for this linewidth. The linewidth requirements for systems with different bit rates and transmission distances are also calculated and discussed. Further, it is seen that by including the second-order dispersion term, the bit rate and transmission distance decreases. For higher linewidths, this decrease in bit rate and transmission distance is very less and vice versa. For 300 MHz linewidth, the decrease in transmission distance is just 30 km, and for 30 MHz linewidth, the decrease is approximately 600 km over significant bit rates.     

Quantum key distribution in an optical fiber at distances of up to 200 km and a bit rate of 180 bit/s

An experimental demonstration of a subcarrier-wave quantum cryptography system with superconducting single-photon detectors (SSPDs) that distributes a secure key in a single-mode fiber at distance of 25 km with a bit rate of 800 kbit/s, a distance of 100 km with a bit rate of 19 kbit/s, and a distance of 200 km with a bit rate of 0.18 kbit/s is described.     

Achieving high bit rate logical stochastic resonance in a bistable system by adjusting parameters

The phenomenon of logical stochastic resonance(LSR) in a nonlinear bistable system is demonstrated by numerical simulations and experiments. However, the bit rates of the logical signals are relatively low and not suitable for practical applications. First, we examine the responses of the bistable system with fixed parameters to different bit rate logic input signals, showing that an arbitrary high bit rate LSR in a bistable system cannot be achieved. Then, a normalized transform of the LSR bistable system is introduced through a kind of variable substitution. Based on the transform, it is found that LSR for arbitrary high bit rate logic signals in a bistable system can be achieved by adjusting the parameters of the system,setting bias value and amplifying the amplitudes of logic input signals and noise properly. Finally, the desired OR and AND logic outputs to high bit rate logic inputs in a bistable system are obtained by numerical simulations. The study might provide higher feasibility of LSR in practical engineering applications.     

基于单光子脉冲时间随机性的光量子随机源

提出了一种基于单光子脉冲时间随机性的光量子随机源。利用衰减成单光子态的光强恒定光源和一个单光子探测器产生单光子随机脉冲,通过连续比较单光子随机脉冲序列中相邻两个脉冲的时间间隔来提取随机位。通过设计高速响应的微通道板单光子探测器和基于现场可编程门阵列(FPGA)的随机位提取电路,获得了超过10Mbit/s的随机位产生速率。通过采用恒比定时和对计数时钟倍频的方法提高时间间隔的测量精度,从而减小随机位序列的相关系数。当光量子随机源的随机位产生速率在10kbit/s以下时,所获得的二进制随机位序列的相关系数小于0.001。运用随机性测试程序ENT和DIEHARD对所获的随机位序列进行测试,测试结果表明序列的随机性非常好且不需要后续处理,完全满足真随机数的标准。     

量子密码通信中量子比特率理论分析

在量子密钥分配中,量子比特率是一个重要的系统参数。通过引入测量因子和筛选因子,建立了基于理想单光子源和泊松分布单光子源的量子比特率理论模型,给出了量子比特率的表达式,并对两种单光子源进行了比较分析。结果表明,当平均光子数大于1时,泊松分布单光子源能被优化。在发射机脉冲重复率一定的条件下,采用泊松分布单光子源无法达到理想单光子源的量子比特率,这是为保密通信所必须付出的代价。     

High-speed transmission limitations due to Polarization Mode Dispersion

In this paper, the impacts of Polarization Mode Dispersion (PMD) on the performance of high-speed optical communication system have been reported at different bit rates. The two systems are modeled using older fibers with same PMD coefficient at different bit rates and third is with the new fiber with less PMD coefficient than that of the previous two. The attenuation, chromatic dispersion and non-linear effects have been disabled, so that all the variation of the results is due to PMD. The bit rate is varied from 2.5 to 40 Gbps and the length is varied from 1000 to 20,000 km. It is shown that the impact of PMD increases with the bit rate of system. It is also reported that the impact of PMD becomes intolerable at the bit rates of more than 40 Gbps. And also the PMD produces very minute impact on the system performance for same bit rate with the variation in the fiber length.     

Experimental characterization of a two-photon memory

We demonstrate the recording of 100 planes of digital images in a page-oriented two-photon memory and characterize the images in terms of signal-to-noise ratio and bit error rate. Possible error sources in the recording are discussed, and methods for compensating for some of these effects are presented. Looking at the distributions of the normalized bit intensities, we are able to estimate the minimum achievable bit error rate for this system.