大口径氘化磷酸二氢钾晶体离线亚纳秒激光预处理技术  

Off-line sub-nanosecond laser conditioning on large aperture deuterated potassium dihydrogen phosphate crystal

作　　者：刘志超[1] 许乔[1] 雷向阳[1] 耿锋[1] 王翔峰[1] 张帅[1] 王健[1] 张清华[1] 刘民才[1] Liu Zhi-Chao;Xu Qiao;Lei Xiang-Yang;Geng Feng;Wang Xiang-Feng;Zhang Shuai;Wang Jian;Zhang Qing-Hua;Liu Min-Cai(Research Center of Laser Fusion,China Academy of Engineering Physics,Mianyang 621900,China)

机构地区：[1]中国工程物理研究院激光聚变研究中心,绵阳621900

出　　处：《物理学报》2021年第7期173-179,共7页Acta Physica Sinica

摘　　要：大口径氘化磷酸二氢钾(DKDP)晶体抗激光损伤性能偏低严重地制约着大型高功率激光装置输出水平.本研究利用离线亚纳秒激光预处理技术有效地提升了大口径DKDP晶体抗激光损伤性能.实际使用情况表明,采用离线亚纳秒激光预处理后,DKDP晶体在9 J/cm^(2)激光通量辐照下的表面平均损伤密度得到大幅下降,由未处理前的5.02 pp/cm^(2)(1pp表示1个百分点)降至0.55 pp/cm^(2),降幅为一个数量级.同时,激光预处理对晶体损伤尺寸具有一定的抑制作用,预处理后晶体损伤点尺寸分布曲线向尺寸减小的方向平移,尺寸分布峰值由预处理前的25μm降至预处理后的18—20μm.The large aperture deuterated potassium dihydrogen phosphate(DKDP)is an important frequency conversion crystal in a large power laser device.There are many defects inside the DKDP bulk material,including the varying element impurities and electronic defects.Comparing with the defect-free material,these bulk defects can easily absorb incident laser energy and pose the risks of initiating damage sites when exposed to high-energy lasers.Beside bulk defects,there are surface defects originating from the DKDP machining process,including cracks,scratches and protuberances.These surface defects affect the damage performance of DKDP crystal by increasing light absorption and weakening local mechanical strength.Due to the defects from both bulk and surface,the actual damage threshold of DKDP crystal is much lower than the expected theoretical value.The lack of its laser damage resistance seriously restricts the laser output power.In this study,the off-line sub-nanosecond laser conditioning technology is proposed to effectively improve the laser damage performance of large aperture DKDP crystal.Its principle is to irradiate DKDP with a mild laser fluence in advance.Although the laser pretreatment cannot directly eliminate the impurities,dislocations,grain boundaries or other macro structural defects in crystals,it indeed changes the distribution and density of intrinsic point defects on a micro-scale.It suggests that the complicated reactions of electron-hole,atomvacancy and the intrinsic point defect annihilation caused by the microstructural transformation of crystal materials under laser conditioning are the possible reasons for reducing absorption and improving the damage resistance.In this experiment,the result of the damage to high-power laser device shows that the mean surface damage density of DKDP crystal at 9 J/cm^(2) decreases from 5.02 pp/cm^(2) to 0.55 pp/cm^(2) after sub-nanosecond laser conditioning.The laser conditioning can remove the protuberance defects on the surface,thus reducing the surface damage den

关 键 词：氘化磷酸二氢钾晶体 亚纳秒激光预处理 激光诱导损伤 高功率激光器 

分 类 号：TQ131.13[化学工程—无机化工] TN249[电子电信—物理电子学]