Author Affiliations
Abstract
1 Joint Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
A direct prejudgement strategy that takes the diffraction ring as the analysis target is put forward to predict hot images induced by defects of tens of microns in the main amplifier section of high power laser systems. Analysis of hot-image formation process shows that the hot image can be precisely calculated with the extracted intensity oscillation of the diffraction ring on the front surface of the nonlinear plate. The gradient direction matching (GDM) method is adopted to detect diffraction rings. Recognition of simulated diffraction rings shows that it is feasible to directly prejudge hot images induced by those closely spaced defects and the defects that are far apart from each other. Image compression and cluster analysis are utilized to optimize the performance of the GDM method in recognizing actually collected diffraction images. Results show that hot images induced by defects of tens of microns can be directly prejudged without redundant information.
diffraction rings gradient direction matching method hot images intensity oscillation High Power Laser Science and Engineering
2018, 6(3): 03000e52
1 中国科学院上海光学精密机械研究所高功率激光物理联合实验室, 上海 201800
2 中国科学院大学, 北京 100049
比较了高通量密度下损伤点分别位于上游介质的前后表面时热像的位置及峰值光强的区别。讨论了热像交替排布的现象及峰值光强随损伤点尺寸的变化规律。针对上游光学元件中的损伤点是诱发后续光路中热像的主要因素, 提出了以损伤点经一定传输距离后引起的衍射环图像为分析对象的热像预判技术。该技术运用高信噪比的梯度方向匹配算法来获取衍射环图像的特征信息, 进而反演出衍射距离和损伤点尺寸。利用液晶空间光调制器产生的单个等效损伤点的衍射图像证明了该方法的有效性; 并采用光学元件上实际存在的损伤点所引起的衍射环图像分析了该算法反演多个损伤点时抑制噪声干扰的能力及其空间分辨率。
激光技术 高通量密度 损伤点 热像 衍射环 梯度方向匹配
中国工程物理研究院流体物理研究所, 四川 绵阳 621900
强激光在液晶材料中传输时易诱导非线性效应, 这种非线性效应对液晶器件光学性能有一定影响。高斯光束通过平行排列的5CB液晶材料后产生自衍射图像, 利用高速相机对不同光强的532 nm激光通过5CB液晶后的衍射图样成像, 获得了从激光作用瞬间到液晶温度达到清亮点附近时衍射图样的变化过程。通过衍射图样对液晶材料光致折射率变化的性质进行了分析。利用基尔霍夫衍射积分公式数值模拟研究了相应强度532 nm高斯光束通过非线性液晶材料后在衍射屏上的衍射图样, 并与实验结果进行了比对, 定性分析了液晶非线性对液晶器件性能的影响。
非线性光学 向列相液晶 衍射环 基尔霍夫衍射积分 光致折射率变化 nonlinear optics nematic liquid crystal diffraction rings Kirchhoff's diffraction integral optical-induced refractive index change
