Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer for LiB3O5 crystal

Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer were investigated for LiB3O5 (LBO) substrate. The design was based on the vector method. The thickness of the inserted SiO2 interlayer could be changed in a wide range for the four-layer design with two zeros at 1064 and 532 nm. The coatings without any interlayer and with 0.1 quarter-wave (λ/4), 0.3λ/4, 0.5λ/4 SiO2 interlayer were deposited respectively on LBO by using electron beam evaporation technique. All the prepared coatings with SiO2 interlayer indicated satisfying optical behavior. This expanded our option for the thickness of an interlayer when coating on LBO substrate. The prepared films with SiO2 interlayer showed better adhesion than that without any interlayer. The thickness of the interlayer affected the adhesion, the adhesion for the coating with 0.5λ/4 SiO2 interlayer was not as good as the other two.     

Wide-angle and broadband graded-refractive-index antireflection coatings

The design and fabrication of graded-refractive-index (GRIN) antireflection (AR) coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.     

多层介质膜脉宽压缩光栅的严格矢量分析

用于展宽和压缩激光脉冲的多层膜脉宽压缩光栅是由多层介质高反膜和位于其顶层的浮雕光栅构成。以设计的高反射多层膜为基础,利用傅里叶模式理论分析了其衍射场分布,给出了TE波自准直角入射的使用条件下,多层介质膜脉宽压缩光栅衍射效率的表达式。以-1级衍射效率为评价函数,分别讨论了HfO2和SiO2为顶层材料时,多层膜脉宽压缩光栅-1级衍射效率高于0.95的光栅结构参量范围。结果表明,在该条件下,选择HfO2为顶层材料时,光栅结构参量有较大的取值范围。给出了优化的光栅结构参量,并分析了光栅制作误差及其使用条件的宽容度,对光栅制作工艺和使用具有一定的指导意义。     

表面热透镜薄膜吸收测量灵敏度提高方法

为提高表面热透镜薄膜吸收测量仪的灵敏度，在表面热透镜衍射理论基础上，通过数值模拟给出了探测激光腰斑半径、探测激光腰斑到样品表面距离、样品到探测光纤端面距离等仪器参数的优化方法. 经优化调整后该仪器能达到优于0.1ppm量级的薄膜吸收率测量灵敏度. 关键词： 吸收测量 表面热透镜 光热形变 薄膜     

基底对光学薄膜弱吸收测量的影响

 对表面热透镜技术测量光学薄膜弱吸收低频调制时不同基底对测量的影响进行了理论分析。用Lambda—900分光光度计测量了K9和石英基底的Ti₃O₅单层膜的吸收值，将该组样品作为定标片；用表面热透镜装置分别测量了BK7和石英空白基底及HfO₂，ZnO两组不同基底不同厚度单层膜样品的吸收。通过分析比较同一工艺条件下镀制的不同基底薄膜样品用与其同种和不同种基底定标片定标测量的结果，表明在低频测量时需要用与测量样品同种基底的定标片定标；不同厚度样品的测量结果表明，在不能严格满足热薄条件时,测量结果需引入修正值。     

Influence of Vacuum Organic Contaminations on Laser-Induced Damage of 1064 nm Anti-Reflective Coatings

We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.     

Intrinsic ZnO films fabricated by DC sputtering from oxygen-deficient targets for Cu（In,Ga）Se2 solar cell application

Samples with nodular defects grown from gold nanoparticles are prepared,and laser-induced damage tests are conducted on them.Nodular defects,which are in critical state of damage,are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope.The crosssectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface,or are even melted.The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress.The numerical results give the critical temperature of the seed region and the thermal stress for crack generation,irradiated with threshold fluence.The numerical results are in good agreement with the experimental ones.     

重复率激光作用下光学薄膜损伤的累积效应

使用脉宽12 ns,频率10 Hz的1064 nm调Q NdYAG激光器,研究了高反射膜在重复率激光作用下的损伤的累积效应.实验发现,高反射膜的损伤阈值随辐照脉冲数增加而降低,表现出明显的累积效应.通过对损伤阈值和损伤概率以及辐照次数的统计性研究,并结合单脉冲辐照的结果,说明了存在于薄膜中微小的缺陷参与了多脉冲激光对薄膜的损伤过程.可用预损伤机制解释实验结果.得到了关于IBS制备的高反射膜的损伤阈值和照射次数的关系式,并用实验结果进行验证,发现具有很好的一致性.实验过程中样品的损伤形貌通过Nomarski偏光显微镜进行了观察,发现是典型的缺陷损伤.     

利用Cramér-Rao理论研究相位差法的最佳离焦量

针对光子数足够多的情况,利用Cramér-Rao理论研究了在选取离焦作为附加像差时,不同的待测波前和目标对最佳离焦量选取的影响。结果表明:在点目标情况下,像差的大小和空间频率对最佳离焦量的影响不大;而在扩展目标情况下,最佳离焦量虽然与待测像差的空间频率关系不明显,但随着待测像差峰谷值的增大而增大。最佳离焦量与目标的结构有关而与其扩展程度关系不大,成像时目标上各点的干扰越大,最佳离焦量越大。     

大口径激光玻璃环抛光学沥青抛光胶

研制了四种不同沥青和松香含量的光学沥青抛光胶,对其形貌、针入度、玻璃化转变温度、软化点和粘度等参量进行了表征。从组成和结构分析了抛光胶三种物理状态变化原因,将玻璃化转变温度和软化点作为其临界转变温度。实验研究了四种抛光胶对大口径激光玻璃的抛光效果,发现抛光胶中沥青和松香的质量分数分别为30%和70%时,抛光效果比较理想,在像散和表面疵病控制方面能够满足要求,可作为大口径激光玻璃抛光专用胶。