摘要
随着光刻技术和低温硅退火等大能量、高功率紫外激光系统的发展,激光装置中窗口材料面临的紫外激光诱导损伤的问题越来越得到重视。MgF_(2)窗口是紫外波段难以替代的光学窗口材料,具有比CaF_(2)更优的紫外透光率、更低的折射率和更高的硬度等优点,因而在高功率紫外激光器、深紫外探测器、光电探测和对抗领域具有重要的应用。研究激光对MgF_(2)窗口材料的损伤机制对推动其在光学领域的应用至关重要。本文通过扫描电镜分析MgF_(2)窗口材料在193 nm紫外激光(2.8 J/cm^(2))辐照下出现的裂纹和凹坑等损伤形貌,随着激光脉冲数和能量的增加,MgF_(2)窗口材料的后表面损伤程度呈指数级增加,窗口材料的后表面损伤程度比前表面更加严重。利用三维时域有限差分(3D-FDTD)方法对193 nm激光辐照MgF_(2)窗口材料内部的激光电场分布进行了计算。模拟发现无论缺陷在前表面还是后表面,电场强度的峰值都出现在后表面附近,后表面更容易被损伤,这与实验结果吻合;缺陷在激光辐照过程中会导致光场的局域调制,增强吸收,同时降低材料表面的机械强度。
MgF_(2) crystal windows for the weakness part of the optical system have obtained much attention due to the rapid development of photolithography and low-temperature silicon annealing.Investigating the mechanism of laserinduced damage on MgF_(2) windows is much more important to push forward its optical applications,which has a few advantages,including lower light transmission,refractive index and higher hardness than CaF_(2) crystals.In this work,the damage morphology induced by the 193 nm excimer laser under a threshold energy of 2.8 J/cm^(2) shows obvious cracks and craters,which were observed by scanning electron microscopy(SEM).As the number and energy of laser pulses increase,damage to the rear surface increases exponentially.Interestingly,the rear surface of the window material was much more severely damaged than the front surface.Here,the electric field distribution of window material under 193 nm excimer laser irradiation was proposed to illustrate the damage physical mechanism,which is calculated by the 3D finite-difference time-domain(FDTD)method.In conclusion,the electric field intensity of the rear surface is stronger than that of the front surface due to defects in the window materials.Therefore,the improvement of optical crystal quality and optical geometry for the high power laser system could be considered to solve the damage problems for the application of MgF_(2) optical windows.
作者
王玺
李欣
赵楠翔
胡以华
李刚
邹路玮
周喻
WANG Xi;LI Xin;ZHAO Nan-xiang;HU Yi-hua;LI Gang;ZOU Lu-wei;ZHOU Yu(State Key Laboratory of Pulsed Power Laser Technology,College of Electronic Countermeasure,National University of Defense Technology,Hefei 230037,China;Anhui Laboratory of Advanced Laser Technology,College of Electronic Countermeasure,National University of Defense Technology,Hefei 230037,China;Institute of Solid State Physics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;School of Physics and Electronics,Central South University,Changsha 410083,China;Hunan Key Laboratory of Nanophotonics and Devices,Central South University,Changsha 410083,China;Powder Metallurgy Research Institute and State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China)
基金
Project(61871389)supported by the National Natural Science Foundation of China
Project(22-ZZCX-007)supported by the Research Major Project of the National University of Defense Technology,China
Project(1908085MF222)supported by the Anhui Province Natural Science Foundation,China
Project(AHL2021ZR04)supported by Foundation of the Anhui Laboratory of Advanced Laser Technology,China
Project(SKL2022ZR10)supported by Foundation of the State Key Laboratory of Pulsed Power Laser Technology,China
Project(JCVKY2023230C010)supported by the National Defense Basic Scientific Research Program of China。
