布儒斯特角法测量金属薄膜折射率并解释不消光现象

根据布儒斯特角原理对磁控溅射的铜膜样品进行了折射率的测量,实验发现当p偏振光以布儒斯特角入射时,反射光并没有完全消光.从理论上、通过数值计算分别论证了金属薄膜折射率的虚部、薄膜界面多次反射等因素的影响,并与实验结果比对得到符合的结果.     

小尺度表面粗糙度与介质吸收对介质折射率测量的影响

将介质表面的小尺度粗糙度等效为覆盖在理想光滑表面上的多层等厚折射率渐变的薄膜,并通过特征矩阵计算多层等效膜模型的P光反射率与入射角的关系.将吸收介质的折射率虚部带入菲涅尔公式进行计算.运用COMSOL Mutiphysics软件对表面粗糙度和介质吸收进行建模和仿真计算.计算结果表明,小尺度表面粗糙度与介质吸收都会导致折射率测量产生误差.分别考虑以布儒斯特角和全反角作为折射率测量的手段,为了得到优于10-5的测量准确度,测量表面粗糙介质的折射率时,采用全反角进行判定;测量具有吸收效应的介质折射率时,采用布儒斯特角进行判定.     

小尺度表面粗糙度与介质吸收对介质折射率测量的影响（英文）

将介质表面的小尺度粗糙度等效为覆盖在理想光滑表面上的多层等厚折射率渐变的薄膜,并通过特征矩阵计算多层等效膜模型的P光反射率与入射角的关系.将吸收介质的折射率虚部带入菲涅尔公式进行计算.运用COMSOL Mutiphysics软件对表面粗糙度和介质吸收进行建模和仿真计算.计算结果表明,小尺度表面粗糙度与介质吸收都会导致折射率测量产生误差.分别考虑以布儒斯特角和全反角作为折射率测量的手段,为了得到优于10~(-5)的测量准确度,测量表面粗糙介质的折射率时,采用全反角进行判定;测量具有吸收效应的介质折射率时,采用布儒斯特角进行判定.     

基于椭圆偏振光谱法的玻璃表面离子束改性分析

采用阳极层线性离子源解离氮气对玻璃表面进行刻蚀处理,研究表面改性后玻璃表面的变化,并分析离化电压对表面粗糙度、折射率以及光学厚度的影响。在此基础上,基于椭圆偏振光谱仪,通过对比不同表面状态下的Δ光谱,讨论固定波长变化入射角的Δ光谱曲线特征与表面折射率、布儒斯特角、粗糙度以及光学厚度之间的关系。结果表明,刻蚀后玻璃的布儒斯特角附近的Δ光谱曲线形状发生变化,突变向高角度偏移,曲线下降斜率增大。通过建模并拟合分析发现,氮离子束轰击使玻璃表面产生光密介质层,表面折射率增大,布儒斯特角增大,粗糙度降低,且随离化电压升高,折射率不变,而光密介质层厚度增加。由原子力显微镜分析表面形貌,验证了离子束对玻璃表面的平整化作用。X射线光电子能谱结果表明离子束使玻璃表面发生选择性溅射,推断光密介质层的产生来自于离子束对玻璃表面的夯实作用。此外,推导并验证了Δ光谱曲线的特征与材料表面状态之间的普适关系,提出了基于椭圆偏振光谱仪的材料表面评估方法,即Δ曲线的突变发生角度增大说明折射率与布儒斯特角的增大;下降斜率增大说明表面粗糙度减小;曲线两端尖角增大说明光学厚度增大。反之亦然。     

用布儒斯特角法同时测定单轴晶体的折射率和光轴方向

在理论上分析了光轴任意方向的单轴晶体的折射率．根据布儒斯特角原理,当线偏振光的电场矢量平行于入射面时,通过测出对样品三个表面的布儒斯特角,就能同时确定单轴晶体的折射率和光轴方向．并利用分光计,在光轴不确定的情况下,测定了方解石的两个主折射率和光轴方向．     

布儒斯特角的测量方法

基于布儒斯特定律和马吕斯定律,利用偏振片的巧妙组合,实现了对介质布儒斯特角和折射率的精确测量.     

光波在左手材料中的菲涅尔公式和布儒斯特定律

根据Maxwell的电磁场理论,推导出单色平面光波入射到介电常量和磁导率分别为ε1、μ1和ε2、μ2的两种介质时的菲涅耳公式和反射率及透射率的普适表达形式.对于ε2<0 和,μ2<0的左手材料,普适菲涅耳公式同样适用.研究了光从右手材料入射到左手材料时反射和折射的特性,给出了反射光为全偏光时布儒斯特角应满足的条件,此条件说明,在左手材料中布儒斯特角不但与折射率有关而且与磁导率有关.     

基底温度对电子束蒸发制备氧化铝薄膜的影响

为了考察基底温度对氧化铝薄膜折射率以及沉积厚度的影响情况,在不同基底温度环境下,通过离子辅助电子束蒸发方式,在玻璃基底上制备了同一Tooling因子条件下所监测到相同厚度的Al2O3薄膜,利用分光光度计测量光谱透过率,依据光学薄膜相关理论,计算了基底温度在25℃～300℃范围内获得的膜层实际物理厚度为275.611 nm～348.447 nm,以及膜层折射率的变化。通过对实验结果的数值计算和曲线模拟,给出了基底温度对于薄膜的折射率和实际厚度的影响情况。     

无标记导模共振布儒斯特传感器检测灵敏度研究

基于严格的耦合波分析方法(RCWA)和等效媒质理论(EMT)研究了布儒斯特角入射时TM偏振光的导模共振特性以及不同结构参数对无标记光学检测灵敏度的影响。分析了三种不同膜层结构对检测灵敏度的影响,通过RCWA计算发现单层光栅在实验入射媒质范围内,折射率每改变0.1,共振角度位置平均变化5.1°,双层膜和三层膜光栅结构对应的共振角度位置平均变化3.6°和4.2°,均表现出了较高的检测灵敏度。在单层光栅结构中,随着光栅调制率由0.4525减弱至0.1441,折射率每改变0.1,角度变化率分别为4.48°和4.95°,检测灵敏度增加。     

转换反射中光自旋霍尔效应的自旋堆积方向

从理论上和实验上研究了转换反射中光自旋霍尔效应的自旋堆积方向的方法,建立了描述光束在空气-棱镜界面反射的自旋堆积模型,揭示了横移与光束入射偏振角的定性关系。研究发现,当入射角小于布儒斯特角时,随着入射偏振角的逐渐增大,自旋堆积的方向发生反转。而当入射角大于布儒斯特角时,自旋堆积的方向不再随入射偏振角的变化而反转。结果表明,在光束入射角为确定值且小于布儒斯特角的情况下,可以通过调控光束的入射偏振角转换自旋堆积的方向。转换自旋堆积方向的研究为有效调控光自旋霍尔效应提供了新的途径。     

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.     

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.     

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.     

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.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.