六氯铅铵晶体相变的拉曼散射研究

在５Ｋ～３００Ｋ温度范围内对六氯铅铵晶体进行了拉曼散射测量，该晶体在Ｔｃ＝７８Ｋ发生从立方结构（Ｏ＾５４）至三方结构（Ｃ＾２３ｉ）的二级相变，ＰｂＣｌ＾２－６八面体Ａ１ｇ模和ＮＨ＾＋４四面体Ａ１模的拉曼频移在Ｔｃ时出现极大值，八面体Ｔ２ｇ模，四面体Ｔ２模和外振动Ｔ２ｇ模在Ｔｃ以下发生连续分裂，另外在Ｔｃ以下观测到对应于高温相ＰｂＣｌ＾２－６八面体Ｔ１ｇ模的软模。     

TEACO2激光器中气体组分对放电状态的影响

采用自制实时取样系统及四极质谱仪测量ＴＥＡＣＯ２激光器放电过程中气体组分变化，分析了测量结果对ＴＥＡＣＯ２激光器放电状态的影响。     

纯金属电阻率的统计模型

本文提出了纯金属电阻率与声子浓度及声子平均动量的平方成正比的统计模型，由此简化模型，给出了纯金属电阻率的一个解析表达式，理论与实验规律相符，即在高温时，电阻率与温度Ｔ成正比，低温时与Ｔ＾５成正比。     

T1系超导体1223相的晶格振动行为研究

对不同铁掺杂量的Ｔ１系１２２３相样品，进行了室温Ｍｏｓｓｂａｕｅｒ谱测量及解谱分析．在７７Ｋ至室温范围作了变温Ｍｏｓｓｂａｕｅｒ谱测量．发现无反冲因子ｆ在Ｔｃ附近反常地下降，表明伴随着超导转变，在Ｔｃ附近晶格振动发生了反常的软化现象．     

大面积超导膜均匀性测量装置

本报道由感应法测量大面积高温超导膜均匀性的装置，其特点是探头可以在液氮温区进行两维移动，从而对大面积膜的不同区域进行测量以达到均匀性测量的目的。测量包括超导转变温度Ｔｃ及临界面电流密度Ｋｃ的测量。     

高温云纹干涉法的进展

本文对云纹干涉法在高温范围的测量应用进行了回顾。对制栅方法、高温云纹干涉光路系统及高温云纹干涉法在材料高温蠕变测量、高温蒸气管道现场蠕变测量、激光焊接残余应变分析等中的应用进行了简述     

高精度OTF标准望远镜的研制

为了建立光学计量标准的需要，研制了光学传递函数标准望远镜。研制中采用了一系列高精度的光学设计、制造和检测技术，本文总结设计原则和设计方法、光学结构参数测量、ＭＴＦ准确计算、ＭＴＦ测量以及ＭＴＦ的不确定度评定等一些关键技术问题。最后，介绍标准望远镜的主要技术性能。实测结果表明，其ＭＴＦ扩展不确定度达到轴上００３，轴外００６，是迄今国际报道的最好结果。     

电子琴频谱的实验研究

介绍一个学生实验，用最基本的频谱分析方法，以ＣＡＳＩＯ ＭＴ－１８电子琴作声源，对其中四种模拟乐器乐音信号的频谱进行测量及分析。     

从动力学驰豫的测量结果推导临界电流密度Jc0（T,Be）的直接方法

本给出了一种从高温超导体动力学驰豫的测量结果推导其临界电流密度Ｊｃ０（Ｔ，Ｂｅ）的直接方法。这种方法与ＧＩＳ相比，避免了ＧＩＳ中所涉及的复杂的讨论和处理，使问题变得直接和明朗。同时，用这种方法还可以从动力学驰豫的测量中求出μ和Ｕｃ随温度和磁场的依赖关系μ（Ｔ，Ｂｅ）、Ｕｃ（Ｔ，Ｂｅ）。     

用连续记录的方法测量高Tc超导材料的转变温度

本文介绍了用连续测量和记录的方法，准确测量高Ｔｃ超导材料的转变温度和实验装置。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.