KDP晶体应力数字式检测方法

使用高精度数字式应力仪测量KDP晶体的应力,给出整体应力分布.通过沿光轴方向测量,消除晶体.光和e光的双折射效应的影响,准确得到晶体材料自身的应力双折射分布.实验结果表明,测量重复性优于0.1nm/cm.对KDP晶体材料应力的高精度数字式检测对于加工和使用具有重要的指导意义.     

KDP晶体柱面生长速率实时测量研究

KDP晶体生长速率高精度地实时测量有助于研究各种因素对晶体生长的影响. 本文用激光偏振干涉法实现了对KDP晶体柱面生长速率和死区的实时测量, 精度达到0.01μm/min. 籽晶 尺寸等实验条件影响测量的结果, 小尺寸(约2mm×2mm)的晶体更有利于死区的表征, 溶解阶段造成的晶体表面位错坑是出现干扰测量的“异常”现象的根源.     

干涉法研究硅酸镓镧单晶的基本性质

用全息干涉法研究了新型压电材料硅酸镓镧的折射率均匀性,利用干涉透过率谱法研究了双折射率.并通过测量透过率,计算了吸收系数.确定了吸收系数与光子能量的变化关系.     

Al~(3+)杂质对KDP晶体光学质量影响的研究

用传统降温法和快速生长法生长了Al3+离子掺杂的磷酸二氢钾(KDP)晶体,并对掺杂的KDP晶体的光学质量进行了测试和分析。实验表明,Al3+掺杂对KDP晶体的透光率没有明显的影响,但会使晶体的光散射加剧,光学均匀性和激光损伤阈值下降。     

锥形六面体BGO大单晶的表面处理与均匀性

闪烁晶体锗酸铋(简称 BGO)的均匀性除依赖于晶体的质量、外形外,还强烈地依赖于晶体表面的性质。本文以(?)×24×(?)cm~3锥形六面体 BGO 大单晶为对象,研究晶体一对粗糙侧面的加工方法和热处理对晶体的光输出、均匀性和能量分辨率的影响,从而确定合适的表面粗糙度及其相应的表面处理工艺,实验结果表明,通过合宜工艺提高了锥形六面体晶体的光输出和均匀性,同时也改善了晶体的能量分辨率。     

晶片干涉中多种光波的叠加问题

光波在晶体表面来回反射形成了多种不同振幅的光波,光波叠加方式的不同会产生完全不同的效果.针对o光与e光非相干叠加和相干叠加两种情况,导出了光强公式.用铌酸锂晶体做了实验,结果与理论十分吻合.这对于分析晶体偏光干涉测量中的干扰以及充分利用干涉图信息改进测量方法与测量精度均具有重要意义.     

会聚偏光干涉测量晶体双折射率

光轴平行表面的晶片的会聚偏光干涉对晶体的双折射率非常敏感。干涉图的对称中心对应于正入射光线,双折射率正比于此点的干涉级md,md的小数部分主要由中央暗条纹的位置决定,md的整数部分由自洽的办法求出。干涉条纹可以用双曲线很好地拟合,使干涉图特征点的提取更为精确。用不同厚度的铌酸锂晶片作了测量,双折射率不确定度为1×10-4。     

光干涉法高精度材料线膨胀系数测量

中国计量科学研究院研制的高精度材料线膨胀系数测量装置,满足温度范围为5～40 ℃、被测件长度在20～1 000 mm之间的线膨胀系数测量。采用激光干涉法测量被测件长度变化量,用高精度温度传感器测量温度值。设计了热平衡式干涉镜,利用空气折射率修正和零位误差补偿技术,保证在5～40 ℃变温范围内激光干涉仪的测量精度。以500 mm标准量块作为测量对象,线膨胀系数测量结果与德国物理技术研究院(PTB)测量结果的相对偏差为0.2%。材料线膨胀系数测量不确定度达到3×10^-8K^-1。     

用偏振干涉仪检定0.01μm位移传感器的初步试验

一、偏振干涉仪法的测量原理传感器的检定是将传感器的测杆与干涉仪的可动镜接触,将由干涉仪测得的可动镜实际移动的距离与由传感器测得的移动距离比较,就得到传感器的示值误差。因此,检定装置的关键是其精度和分辨率高于传感器的干涉仪。干涉仪的光路图见图1,从激光器发出的线偏振光与偏振分光镜的水平轴成45°角的方向入射,经偏振分光镜分成S光和P光,分别经参考镜和可动镜反射后,再次在偏振分光镜处会     

基于慢光技术的 M-Z干涉仪光频率检测技术

利用一维光子晶体波导慢光和正交信号处理技术,提出了一种具有高灵敏度和宽测量范围的慢光马赫-曾德干涉仪光频率检测系统。理论分析表明,正交信号处理技术可以消除M-Z干涉仪测量灵敏度与测量范围间的矛盾。然后,通过有限时域差分法对一维光子晶体波导结构进行分析和优化,在750GHz光频率范围内,获得了群折射率为10.7的慢光,使M-Z干涉仪的光频率测量灵敏度提高了10倍。最后,利用4×4耦合器搭建了实验系统,将测量范围提高到原干涉仪的6倍。     

Robust and accurate estimate of the orientation of partially polarized light from a camera sensor

Polarized light carries valuable information about where the light has been and the various physical parameters that have been acting upon it. Thus there are several methods in computer vision that make it possible to obtain information on the observed object by studying the polarization of light reflected on the object. Most studies using this principle are interested in the determination of the object orientation in three-dimensional space. The basis of these studies rests on the estimate of a parameter that connects the orientation of the observed surface and the polarization of the reflected light wave. This parameter is the angle of polarization phi, also called the orientation of polarization. Generally, one using these methods estimates the phi angle by observing the reflected light wave through a linear polarizing filter and grabbing multiple frames for different angular orientations of the polarizer. So, between each acquisition, the polarizer is rotated of an angle theta relative to a horizontal reference axis. The accuracy of the phi estimate is then directly related to the positioning of the polarizer. But, in practice, it is difficult to guarantee the exact value of the rotation of this polarizer. It is all the more difficult to guarantee the reliability of positioning in time. We thus propose a robust and accurate solution, based on the self-calibration principle, for measuring the orientation of partially polarized light using CCD cameras. In contrast to methods generally discussed in computer vision journals, our estimate of the angle of polarization is independent of the reliability of the polarizer positioning.     

Refractive-index measurements of natural air-hydrate crystals in an Antarctic ice sheet

The refractive index of air-hydrate crystals found in a deep Antarctic ice sheet was measured for the first time, as far as we know, using a Mach-Zehnder interferometer. A small difference between the refractive indices of the air-hydrate crystals and the matrix ice crystal was measured by the fringe-shift method. It was found that the refractive indices of all air-hydrate crystals were larger than those of ice, and the average difference was 5.3 × 10(-3), even considering the refractive-index anisotropy of ice crystals. Because the refractive indices depend on the occupancy ratio of cagelike cavities by air molecules, we compared the experimental results with the calculated values using the Onsager cavity model. We determined that the present method is useful for estimation of the cavity occupancy ratio of air-hydrate crystals and also of the amount of air molecules in polar ice cores.     

Polarizing properties of embedded symmetric trilayer stacks under conditions of frustrated total internal reflection

An all-transparent symmetric trilayer structure, which consists of a high-index center layer coated on both sides by a low-index film and embedded in a high-index prism, can function as an efficient polarizer or polarizing beam splitter under conditions of frustrated total internal reflection over a wide range of incidence angles. For a given set of refractive indices, all possible solutions for the thicknesses of the layers that suppress the reflection of either the p or s polarization at a specified angle, as well as the reflectance of the system for the orthogonal polarization, are determined. A 633 nm design that uses a MgF2-ZnS-MgF2 trilayer embedded in a ZnS prism achieves an extinction ratio (ER) > 40 dB from 50 degrees to 80 degrees in reflection and an ER > 20 dB from 58 degrees to 80 degrees in transmission. IR polarizers that use CaF2-Ge-CaF2 trilayers embedded in a ZnS prism are also considered.     

Wide-angle, high-extinction-ratio, infrared polarizing beam splitters using frustrated total internal reflection by an embedded centrosymmetric multilayer

A centrosymmetric multilayer stack of two transparent thin-film materials, which is embedded in a high-index prism, is designed to function as an efficient polarizer or polarizing beam splitter (PBS) under conditions of frustrated total internal reflection over an extended range of incidence angles. The S(LH)(k)LHL(HL)(k)S multilayer structure consists of a high-index center layer H sandwiched between two identical low-index films L and high-index-low-index bilayers repeated (k times) on both sides of the central trilayer maintaining the symmetry of the entire stack. For a given set of refractive indices, all possible solutions for the thicknesses of the layers that suppress the reflection of p-polarized light at a specified angle, and the associated reflectance of the system for the orthogonal s polarization, are determined. The angular and spectral sensitivities of polarizing multilayer stacks employing 3, 7, 11, 15, and 19 layers of BaF(2) and PbTe thin films embedded in a ZnS prism, operating at lambda=10.6 microm, are presented. The 15- and 19-layer stack designs achieve extinction ratios (ER) >30 dB in both reflection and transmission over a 46 degrees -56 degrees field of view inside the prism. Spectral analysis reveals additional discrete polarizing wavelengths other than the design wavelength (lambda=10.6 microm). The 11-, 15-, and 19-layer designs function as effective s-reflection polarizers (|R(s)|(2)>99%) over a 2-3 microm bandwidth. The effect of decreasing the refractive index contrast between the H and L layers on the resulting ER is also considered.     

Characterization of the influence of polarization orientation on bulk damage in KDP crystals at different wavelengths

The investigation of polarization orientation on damage performance of type I doubler KDP crystals under different wavelengths pulses irradiation is presented in this work. Pinpoints densities (PPD) and the size distribution of pinpoints are extracted through light scattering pictures captured by microscope. The obtained results indicate that the measured PPD as a function of the fluence is both wavelength and polarization dependent, although neither fluence nor polarization have impact on the size distribution of pinpoints. We also find that the damage performances can separate into three groups depending on the wavelength, which suggests the existence of different categories of precursors and different mechanisms responsible for bulk damage initiation in SHG KDP crystals.     

Linear and nonlinear optical properties of KDP crystals with incorporated Al2O3⋅nH2O nanoparticles

Optical and nonlinear optical properties of a novel composite system based on KDP single crystals with embedded nanoparticles of nanostructured oxyhydroxide of aluminum (Al₂O₃·nH₂O, NOA), were studied. KDP crystals with NOA nanoparticles (KDP:NOA) possess high optical quality and homogeneity. Optical spectroscopy showed the presence of an absorption band at 270 nm caused by NOA nanoparticles incorporated in the KDP matrix. There was observed an enhancement of nonlinear refractive index and inversion of its sign in KDP:NOA crystals in comparison with nominally pure KDP crystals under excitation of picosecond laser pulses. The obtained results demonstrate that KDP:NOA is a promising composite material for optoelectronics and nonlinear optics.     

Effect of interfacial refractive index on optical molecular orientation measurements

The sensitivity of optical molecular orientation measurements to assumptions regarding thin film refractive index was investigated. Specifically, the influence of the interfacial refractive index on second harmonic generation (SHG) and linear dichroism measurements made in a total internal reflection (TIR) geometry was probed for five distinct molecular systems. The five molecular thin films ranged from weakly adsorbed species in equilibrium with solution to covalently bound molecules. Polarization data from the two techniques were fit using a range of assumed interfacial refractive indices. Surprisingly, a linear relationship between the difference in calculated apparent orientation angle and the difference in solvent-prism refractive index was observed. The trend indicates that for a TIR geometry, the error introduced by the thin film refractive index is negligible when the difference in solvent and prism refractive indices is less than approximately 0.08. However, there are clearly cases, such as a glass/air interface, in which assumptions regarding the thin film refractive index can result in significant error in the extracted orientation angle.     

KDP晶体全外围夹持方案理论分析

在超大超薄KDP晶体紧密装校过程中,由于夹持力与重力作用,导致晶体面形发生形变.本文提出了KDP晶体全外围夹持方案,并对KDP晶体垂直状态下的各种受力模型进行应变分析.理论分析结果表明:对称支撑与均匀施力对晶体面形影响较大;当满足对称支撑和均匀施力的情况下,上侧面四个胶钉施力小于25N时,能够满足在线物理实验要求.     

Self-referenced rectangular path cyclic interferometer with polarization phase shifting

A polarization phase shifting interferometer using a cyclic path configuration for measurement of phase nonuniformities in transparent samples is presented. A cube beam splitter masked by two linear polarizers is used to split the source wavefront into two counter propagating linearly polarized beams that pass through the sample. At the output of the interferometer, the two orthogonally polarized beams are rendered circularly polarized in the opposite sense through the use of a quarter wave plate. Finally, phase shifting is achieved by rotating a linear polarizer before the recording plane. In a rectangular path interferometer, although the two counter propagating wavefronts are laterally folded with respect to each other in the interferometer arms, the beams finally emerge mutually unfolded at the output of the interferometer. This phenomenon is utilized to create a reference if the sample is introduced in one lateral half of the beam in any one of the interferometer arms. The polarization phase shifting technique is used to generate four phase-shifted interferograms, which are utilized to evaluate the phase profile of the phase sample. Experimental results presented validate the proposed technique.     

Interferometric array illuminator with analysis of nonobservable fringes

Interferometric methods for array generation offer various advantages over diffractive methods. Use of polarizing elements in an interferometric array illuminator results in interesting properties in addition to improving the efficiency considerably from low levels. The array pattern appears as nonobservable fringes that can be observed only with a polarizer, and the interferometer is insensitive to one of the tilt components. A thorough analysis of such an interferometric array illuminator is presented in this paper. Several possible applications of such an interferometer in addition to use as an array illuminator are proposed.