基于空间分辨法分析时间低相干光自聚焦效应  

Low-temporal coherence light self-focusing effect by spatial resolved method

作　　者：单翀 孔令豹 崔勇[2] 季来林[2] 赵晓晖 李福建 饶大幸 赵元安[3] 隋展 邵建达[3] Shan Chong;Kong Ling-Bao;Cui Yong;Ji Lai-Lin;Zhao Xiao-Hui;Li Fu-Jian;Rao Da-Xing;Zhao Yuan-An;Sui Zhan;Shao Jian-Da(Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing,School of Information Science and Technology,Fudan University,Shanghai 201203,China;Shanghai Institute of Laser Plasma,China Academy of Engineering Physics,Shanghai 201800,China;Key Laboratory of High Power Laser Materials,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China)

机构地区：[1]复旦大学信息科学与工程学院,超精密光学制造工程技术研究中心,上海201203 [2]中国工程物理研究院上海激光等离子体研究所,上海201800 [3]中国科学院上海光学精密机械研究所强激光材料重点实验室,上海201800

出　　处：《物理学报》2024年第9期36-45,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12074353)资助的课题

摘　　要：时间低相干光由于其瞬时宽带的物理特性,在激光惯性约束聚变中得到了广泛的关注.然而其复杂的时间尖峰结构或将诱导非线性自聚焦效应的放大.同时,传统的非线性自聚焦特征数值的测试方法中,多数材料的表面损伤先于体内自聚焦成丝损伤发生,这为对比不同激光的非线性效应带来巨大影响.本文利用短焦距透镜对熔石英进行紧聚焦,通过调节入射激光能量,在避免前表面损伤的前提下,诱导熔石英产生自聚焦成丝损伤.随后通过理论计算对光束在样品体内传输过程的光斑变化进行空间分辨处理,并得到对应细分位置的非线性数值.最终将各个位置对应的非线性相位变化值进行积分,得到前表面无损条件下材料的非线性自聚焦特征数值.测试结果表明时间低相干光的非线性自聚焦效应比传统单模脉冲激光更强.本文不仅设计了一套更加精确的对比不同激光非线性效应的测试方法,同时也探明了时间相干性对于非线性自聚焦效应的影响机制,为高功率时间低相干激光器的设计提供理论依据和参考.The low-temporal coherence light(LTCL)has received extensive attention in the research of inertial confinement fusion due to its physical properties of instantaneous broadband.Recent reports demonstrated that the LTCL has significant suppression effects on laser plasma instability.However,the temporal spike structures of the LTCL will not only induce the amplification of the self-focusing effect,but also make its small-scale self-focusing characteristics and corresponding damage mechanism more complicated.Exploring the self-focusing characteristics of the LTCL will provide an important information for improving the output power of the LTCL.In this work,we design a more accurate test method for comparing the nonlinear self-focusing effects of different lasers,and compare the self-focusing effect of LTCL with single longitudinal mode(SLM)pulse.In the experiments,fused silica is tightly focused by a short focal length lens to avoid damaging the input surface.A spatially resolved test method is designed to measure the nonlinear I×L value(where I is the incident intensity,L is the distance from the head of filamentation damage to the input surface),which is accumulated from the input surface to the head of filamentation damage.The results show that the nonlinear I×L value obtained by the spatially resolved method is lower than by the traditional test method,since the energy loss caused by incident surface damage and backward stimulated Brillouin scattering(SBS)has been resolved.Furthermore,the nonlinear I×L values of the SLM pulse and the LTCL are also compared by the traditional test method and spatially resolved method.The test results show that due to the temporal spike structure,the LTCL has a lower nonlinear I×L value than the SLM pulse.The SBS effect and the different damage characteristics of the input surface are also analyzed.This study provides a more accurate test method for better analyzing the self-focusing effect of LTCL and laser pulses with different characteristics,and hence presenting a reference

关 键 词：惯性约束核聚变 时间低相干光 非线性自聚焦 特征数值 空间分辨法 

分 类 号：TL62[核科学技术—核技术及应用]