基于光热敏折变玻璃的透射型体布拉格光栅角度选择性研究

采用Kogelnik耦合波理论讨论了透射型体布拉格光栅(TVBG)的角度选择特性;结合分波面双光束干涉法和两步热处理法在光热敏折变玻璃中制备了周期为1 μm的TVBG,TVBG相对衍射效率可达91.1%;利用发散光束研究了TVBG的角度选择特性,验证了TVBG具有良好的角度选择特性,可以应用于角选择滤波,抑制中高频调制,提高激光的近场均匀性。     

体布拉格光栅用于高功率光谱组束的研究

使用透射型体布拉格光栅组束两束光纤激光,实现了856 W光谱组束输出。总的光谱组束效率为73.7%,组束光束的横向质量因子为7.9,纵向质量因子为2.7。研究结果显示,虽然体光栅的角色散严重影响衍射光束的光束质量,但其并不影响透射光束的光束特性。由于当前宽谱光纤激光器的输出功率远大于窄线宽输出,使用宽谱光纤激光器(光谱带宽超过4nm)作为透射光束,能够在不降低组束效率和组束光束质量的前提下,有效提升使用体布拉格光栅进行光谱组束的总输出功率。     

激光光斑漂移的检测

针对激光光斑漂移设计了一套光斑漂移检测系统。利用该系统实现了对He-Ne激光器出射光束漂移的检测。它采用CCD摄像头和图像采集卡采集激光器输出光斑，通过专门软件对数字图像进行处理，得出光斑漂移的大小；另外，利用几何光学方法得到了激光光束在X方向、Y方向以及空间立体角上的漂移大小。分析了引起光束漂移的原因。结果表明：He-Ne激光器出射光束的指向主要受温度、环境振动、空气扰动和激光器自身结构的影响。该系统能准确地测量出激光器出射光束的漂移大小，实现光束漂移的控制。     

基于Zemax的He-Ne激光光束聚焦物镜的设计

 为了得到一个合理的He-Ne激光光束聚焦物镜,采用以正前凸型为基础的高折射率双片结构,应用Zemax软件进行优化设计,获得了弥散斑直径为0.002mm的He-Ne激光聚焦物镜,该镜头只需校正轴上点球差。实验结果表明：设计的镜头比低折射率单片透镜得到的弥散圆直径更小,达到0.0019mm,球差被控制在-0.05mm～+0.05mm范围内,MTF曲线所围面积变大,中心点亮度增高,符合实际需要。     

激光光幕式压力机械光电保护装置的研究

以激光束形成光幕为压力机械提供一种光电安全保护装置。这种以Ｈｅ－Ｎｅ激光束形成的光幕配以相应的电子电气元件构成的安全保护装置，简单可靠。。实现了保护高度４００ｍｍ，长度６ｍ，光轴间距３０ｍｍ的灵敏区，及稳定的安全保护功能。     

Back-reflection effects in a frequency-stabilized two-mode He-Ne laser

We investigated the behavior of a frequency-stabilized 1 mW two-mode helium-neon laser in the presence of optical feedback. In this paper, we presented how the amplitude and frequency shift of the returning beam influence operation of the laser. We showed the conditions under which the He-Ne laser work is unstable and stable in frequency and where it is insensitive to the returning beam. We also showed how much the frequency of the returning beam has to be shifted in order to reduce the sensitivity of the laser on the back-reflection.     

Uniphase1007型He—Ne激光管的纵向塞曼稳频研究

本文介绍采用拍频曲线晶振基准法首次在Uniphase 1007型长寿命商品He-Ne激光管上实现了无压电陶瓷调谐元件的塞曼双频稳频,采用可调永磁供磁,达到光频长期漂移5×10~(-9);双频双线偏振分离度1/60;双线偏振正交度89.5°;入锁及锁定情况良好.给出了塞曼双频激光器的调试技术.描述了输出光束偏振状态和纵模数关系的一个物理现象.     

Two-dimensional angular filtering by volume Bragg gratings in photothermorefractive glass

We propose and perform two-dimensional angular filtering on the basis of volume Bragg gratings (VBGs) in a series connection for cleaning up a laser beam. The dependence between angular selectivity and VBG parameters is analyzed with the coupled wave theory. Near-field modulation, contrast ratio, and power spectral density were used to evaluate the effect of filtering in both the spatial and frequency domain. The results from our initial experiments showed that the near-field modulation and contrast ratio of laser beam were remarkably improved.     

高功率激光系统中近场滤波设计与理论模拟

基于经典耦合波理论,分析了透射型体Bragg光栅的衍射特性,建立了透射型体Bragg光栅的设计体系。采用带有调制的超高斯光束,对高功率激光系统的近场滤波进行了理论模拟,采用软化因子、近场调制度、近场对比度分析了输出光束的近场质量,采用功率谱密度函数分析了近场滤波对不同空间频率的滤除能力。研究结果表明,近场滤波对0.3～2.0mm-1的中、高频调制具有显著的滤除作用。     

Signal recording in acoustooptical imaging of scattering media

An expression for a signal at the ultrasonic frequency from a photodetector arising when diffraction waves at the cathode mix is obtained for the case when the optical and acoustic beams are space-limited and Bragg angles are small. The alternating current generated when the scattering medium is crossed by a focused 3-MHz ultrasonic beam and illuminated by a cw He-Ne laser is measured. Satisfactory agreement between experimental results and those calculated from the formulas obtained indicates that our model treating acoustooptical interaction in the medium in terms of Raman-Nath diffraction is valid. Conditions for measuring the alternating current (which is a parameter of acoustooptical imaging) that are optimal from the viewpoint of maximizing the signal and signal-to-noise ratio are predicted theoretically and corroborated experimentally.     

Kinetics of Anisotropic Scattering and Optical Turbulence upon Laser Irradiation of AgCl:Ag Films

The kinetics of anisotropic scattering and optical turbulence upon formation of quasi-periodic structures (QPSs) in photosensitive composite AgCl:Ag films irradiated by Gaussian beams of a He-Ne laser is studied. The buildup kinetics of the scattering induced by an unfocused beam is used to find the threshold exposures for the formation of QPSs and an additional spatiotemporal instability resulting from interaction between the gratings during their development. It was established that there exists a threshold for the formation of a strong instability (optical turbulence) when the QPSs are induced by a focused beam. The decay curves of the mean frequency of the chaotic intensity oscillations, as well as the dependence of this frequency on the beam power, are obtained under conditions of turbulence. It is shown that both the turbulence and its decay are controlled by a competition between the microgratings in the QPSs and by gradual widening of the area of active competition under the action of the Gaussian beam. The AgCl:Ag films are shown to be capable of rapidly and repeatedly rearranging the QPSs and the spatial orientation of the anisotropic scattering upon variation of the direction of linear polarization of the laser beam.     

Engineering Optimisation: An Introduction with Metaheuristic Applications,by Xin-She Yang

When a beam of high intensity laser light is scattered by the fluctuations spontaneously existing within a fluid medium a spatial modulation of the dielectric constant may be induced. The role of such a modulation in causing stimulated scattering of the intense laser beam or Bragg reflection of any weak independent probe beam is discussed and theoretically analyesd. It is shown that such Bragg reflection provides a convenient technique for the study of the modulation. Experimental observation and investigation of Bragg reflection from such a modulation is described. A related technique has been used to investigate the development of light induced periodic structures on surfaces.     

全内腔绿光He-Ne激光器

采用Needle法,对全内腔绿光He-Ne激光器膜系进行设计,并给出了所设计膜系的光谱性能。利用离子溅射镀膜技术镀制了所设计的膜片并且给出了测量结果。制备了多种规格的全内腔绿光He-Ne激光器并且讨论了相关工艺。其中腔长420mm的全内腔绿光He-Ne激光器的典型输出光功率为3mW（单模）,腔长360mm的典型输出光功率为2mW（单模）,腔长240mm的典型输出光功率为1mW（单模）,腔长100mm的小短管子也能有0．1mw的出光功率。     

纵模分裂式正交偏振双频He-Ne激光器

在激光器谐振腔中放入单轴石英晶体,由于石英晶体对o光和e光的折射率的不同,所以,在同一谐振腔中o光和e光有不同的光程和谐振频率.将其称之为模式分裂效应.利用这一效应可以制成频率达几十兆赫兹的双频激光器.针对原有理论与实验结果之间的某些差异,建立了一套分析该种类型双频激光器的理论.根据所建立的理论着重分析了谐振腔光轴与晶轴夹角α对激光器频差的影响.并绘出了He-Ne激光管L<150nm和150nm相似文献   

激光等离子体球面晶体光谱成像

 利用自聚焦原理,研制了一种新型的球面弯晶谱仪。晶体分析器采用云母材料,其弯曲半径为380 mm,布拉格角为51°。利用成像板接收光谱信号,其有效面积为30 mm×80 mm,从等离子体源经晶体到成像板的光程长为980 mm。物理实验在中国工程物理研究院激光聚变研究中心20 J激光装置上进行,入射激光能量为6.78 J,成像板获得了铝激光等离子体X射线的光谱空间分辨信号。球面云母弯晶谱仪的光谱分辨率达到1 000～1 500,在相同环境放置的PET平晶的光谱分辨率为50～100。结果表明：球面弯晶具有较高的光谱分辨率和信噪比,适合于激光等离子体X射线的光谱学研究。     

In Situ Determination of Macroparticle Velocities in a Copper Vacuum Arc

The velocity components of individual macroparticles (molten droplets) moving through the interelectrode plasma of copper vacuum arc were measured by applying the forward-scattering laser Doppler anemometry method (LDA). The arc was sustained between two cylindrical copper electrodes, 14 mm in diameter and spaced 4 mm apart. Two current waveforms, with rise times to peak currents of 1 and 6 ms and duration of about 5 and 30 ms, respectively, were used in the experiment, while in both cases peak currents were either 1 or 2 kA. Macroparticles traversing through the ellipsoid shaped "probe-volume," which was produced by the intersection of the two He-Ne laser beams, scattered the laser light, through a monochromator, used as a 1.7-A bandpass filter, onto a photomultiplier. The Doppler-frequency component of the photomultiplier was recorded after appropriate filtering and amplification. The macroparticle velocity component obtained from the Doppler frequency was in the plane defined by the illuminating laser beams and directed perpendicularly to the optical axis. Macroparticles were detected during the whole period of the discharge, and their velocity was determined either at the instant of peak current or when the current decreased to 10 percent of its peak value, at several spatial locations inside the discharge volume. The measured macroparticle velocity components ranged from about 10-20 m/s up to about 700 m/s, showing a systematic dependence on the instantaneous value of the arc-current and on the spatial position of the "probe-volume," e. g.     

反射式液晶空间光调制器电控光束偏转

为获得较大的光束电控偏转范围,使用空间分辨力高达8 m的反射式液晶空间光调制器实现了对入射632 nm激光的电控偏转。利用双光束共焦干涉方法测量了液晶空间光调制器的电控相位延迟特性,最大相移量可达3。根据二元光学理论和器件的电控相位延迟特性,设计了周期台阶相位模式和相应的加载灰度图,以最大衍射效率实现对入射光束的闪耀电控偏转。结果表明:相位模式台阶数为8时,可以实现10 mrad的光束偏转,闪耀级次衍射效率可达46%。利用二元光学的衍射模型对影响衍射效率的关键因素进行了分析,认为器件较低的填充因子和周期台阶模式相位重置点诱导的指向矢回程区是限制光束衍射效率的主要因素。     

双频氦氖激光回馈位移测量系统的实验与应用研究

研究了一种全新的纳米尺度位移测量系统。将双折射元件插入He-Ne激光器谐振腔内产生频率分裂效应，使原本单模谐振的激光器输出变成了频差可调的2个正交偏振频率（o光和e光），而形成双频激光器。在激光谐振腔外放置沿激光轴线位移的反射表面，将输出的激光束反射回腔内，以便对激光的光强进行调制，可实现高分辨率非接触式可判向位移测量。提出了一种细分方法，该方法突破了传统干涉系统的衍射极限（1/2波长）。对于633nm波长He-Ne激光，本系统的理想分辨率为1/8波长（约为79nm）。     

Effect of delay of the thermocapillary response of a transparent liquid layer during laser heating of the absorbing substrate

The effect of delay in the thermocapillary response of a transparent liquid layer on an absorbing substrate during its heating by a laser beam is discovered. The response is an interference pattern formed on a screen placed in the beam cross section by the beam reflected from a thermocapillary dip. It is found that the delay time of the response of a thin (h < 1.8 mm) layer of a liquid in a viscosity range of 3–6 mPa s to a 20.9-mW exciting beam from a He-Ne laser (λ = 633 nm) is proportional to the squared layer thickness with a proportionality factor depending on the viscosity and thermal diffusivity of the liquid.     

基于正交偏振双纵模的氦氖激光器纳米测尺系统

提出一种基于正交偏振双纵模的氦氖激光器纳米测尺系统,将双折射元件插入He-Ne激光器谐振腔内产生频率分裂效应,使激光器变成了频差可调的双频激光器。运用频率分裂、模竞争、双纵模功率调谐等激光物理效应和设定浮动阈值,研制了新型的激光器纳米测尺。以激光波长为尺子,具有可溯源性,在没有任何电细分的条件下达到了纳米量级的分辨率,与激光干涉仪的比对实验表明,该系统的分辨率为79 nm,量程为15 mm,线性度为5.4×10-5,标准差为380 nm。