基于分光计多光源三棱镜色散特性综合实验的探究性研究

当光线传播到不同介质界面如平面镜、三棱镜等的光学表面时,会发生反射、折射现象,光线的传播方向将发生改变,在入射光和出射光之间产生一定的夹角。以分光计作为精确测量角度的光学仪器,分别在氢灯、氦灯、钠灯和汞灯几种不同光源照射下,选取对应光源中清晰且能够准确确定位置和波长的谱线,分别采用最小偏向角测量法和掠入射法,测量出不同频率单色光在三棱镜中的折射率,建立色散特性经验公式,获取的三棱镜色散特性规律符合柯西色散公式。研究结果对于基于分光计调节的设计研究性、系列专题实验等探究性教学具有一定的指导意义。     

利用色散法探索玻尔氢原子理论测量普朗克常数

普朗克常数是物理学中一个重要的常数,利用测角仪器分光计,探索用玻尔氢原子理论来测普朗克常数。根据最小偏向角测量三棱镜折射率的原理,利用分光计测量三棱镜的折射率来研究光的色散规律,测量棱镜材料对不同波长入射光的折射率,得到棱镜材料的色散曲线和拟合方程。根据玻尔的氢原子理论,用分光计测出氢原子光谱四条谱线（α,β,γ,δ）的偏向角对应的折射率,由科西经验公式计算出相应的波长。     

基于三种色散公式的三棱镜色散实验研究

利用分光计得到了汞灯透过三棱镜后五种不同谱线的最小偏向角,计算出了它们的折射率,基于Cauchy,Hartmann,Conrady三种色散公式,拟合得到了三种不同色散公式的的色散系数和色散曲线。     

汞光谱色散规律的实验研究

在分光计实验中,低压汞灯发出五种不同波长的单色光经玻璃三棱镜后发生色散现象,实验研究表明玻璃三棱镜对汞光源光谱折射率是随波长增大而减小的变化的规律,其中对黄光折射率最小,紫光折射率最大,这种色散属于正常色散,通过这个实验进一步说明了科希公式的正确性.     

分光计实验中棱镜折射率色散 研究的实验拓展

在分光计实验教学过程中,在完成自准法测量三棱镜的顶角的基础上,让学生把实验中能够清晰观察到的汞灯棱镜光谱中不同波长谱线对应的折射率利用最小偏向角法进行测量,再利用正常色散的柯西经验公式对数据进行拟合,作出n-λ曲线并求出所用材料(三棱镜)的系数A、B、C。通过上述实验内容的拓展,不仅让学生进一步熟悉了最小偏向角法测量三棱镜玻璃折射率的实验操作方法,而且让学生对棱镜玻璃波长色散的物理含义有了定量上的深入理解。     

Origin软件在研究三棱镜色散关系与色散率曲线中的应用

结合光栅测光波波长和分光计测三棱镜玻璃的折射率两个普通物理实验,将观测到的11条谱线的相关数据利用Origin软件进行自定义非线性拟合、绘图、微分等功能,得出三棱镜色散关系函数以及色散曲线,对色散曲线微分得出色散率曲线,展示了 Origin软件在物理实验数据处理中的高效、准确和科学性。     

三个零色散波长光子晶体光纤及相位匹配特性

利用多极法对光子晶体光纤的色散特性进行了模拟,通过结构参数的精确设计,得到了具有三个零色散波长的单模光纤,获得了色散值极低的超平坦色散曲线。对三个零色散波长光子晶体光纤特殊的相位匹配特性进行了研究,在不同光纤结构参数下,得到了相位匹配波长随抽运波长及抽运功率的变化规律,分析了不同色散曲线对应的相位匹配波长特点。三个零色散波长光纤能实现两个反常色散区之间光孤子的高效波长变换,可以获得6个新的四波混频相位匹配波长,产生更多光子对,为高效、多波长四波混频的产生及超连续谱的研究提供了新的物理环境。     

连续谱全反射法研究三棱镜折射率色散特性

利用连续光谱全反射法,研究了三棱镜的折射率色散特性,增加了测量波长数目.利用最小二乘法进行曲线拟合,给出三棱镜折射率的柯西表达式.     

具有三个及四个零色散波长光子晶体光纤的仿真研究

利用多极法对光子晶体光纤的色散特性进行了模拟, 通过设计合适的结构参数, 得到了具有3个零色散波长的单模光纤.对中心纤芯有1个微小空气孔光子晶体光纤的色散特性进行了分析, 设计出了具有4个零色散波长的色散曲线.分析了零色散波长随光纤结构的变化规律, 这些零色散波长的位置和间距可以在很大波长范围内灵活调节. 具有多个零色散波长的光纤可以得到色散值极低的超平坦色散曲线. 多个零色散波长光纤能产生丰富的相位匹配曲线, 可以有效地控制光孤子及超短脉冲的四波混频及共振散射产生的光谱特性.     

棱镜法测量水的色散

本文改进了测量液体折射率的一种方法，由原先对单色波长光源测量液体折射率发展为用复合光源（汞灯）直接测量色散．在原先两个等边三棱镜之间加入液体膜，在利用全反射原理的基础上，增加了一个棱镜用于产生色散．测出了水对于不同波长的光的色散，与文献对照不确定度在0．1％以内．最后对这种测量方法作了讨论．     

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.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

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.