缓冲层对LBO晶体上1 064 nm|532 nm二倍频增透膜的激光损伤阈值的影响

采用电子束蒸发方法在LBO晶体上制备了无缓冲层和具有不同缓冲层的1 064 nm，532 nm二倍频增透膜.利用Lambda900分光光度计和调Q脉冲激光装置对样品的光学性能和抗激光损伤性能进行了测试分析.结果表明，所有样品在1 064 nm和532 nm波长的剩余反射率都分别小于0.1％和0.2％.与无缓冲层样品相比，采用SiO2和MgF2缓冲层薄膜的激光损伤阈值分别提高了23.1％和25.8％，而Al2O3缓冲层的插入却导致薄膜的激光损伤阈值降低.通过观察薄膜的激光损伤形貌,分析破斑的深度信息和电场分布，表明LBO晶体上1 064 nm，532 nm二倍频增透膜的激光损伤破坏主要表现为膜层剥落，激光产生的热冲击应力使薄膜应力发生很大变化，超过膜层之间的结合而引起膜层之间的分离.采用SiO2或MgF2缓冲层可改进Al2O3膜层的质量，从而有利于提高薄膜的激光损伤阈值.

Influence of Buffer Layer on Laser - induced Damage Threshold of 1 064 nm,532 nm Frequency-doubled Antireflection Coating for LBO

1 064 nm,532 nm frequency-doubled antireflection coating with no buffer layer or with different buffer layers were fabricated by using electron beam evaporation technique on LBO.The optical property and laser-induced damage threshold (LIDT) were investigated by Lambda900 spectrometer and Q-switch pulse laser,respectively.The results shown that the reflectance of all samples is below 0.1% and 0.2% at wavelength of 1 064 nm and 532 nm,respectively.Comparing with the sample of no buffer layer,LIDT of the coatings are improved by 23.1% and 25.8% using buffer layer of SiO2 and MgF2 and that of the coating with buffer layer of Al2O3 is decreased.By analyzing the morphology,depth information of laser-induced damage zones and electric field distribution of the film stacks,it is found that the laser - induced damage of 1 064 nm,532 nm frequency-doubled antireflection coating for LBO mainly exhibite spallation of a plated film under irradiation of a laser beam because the stress of the coating exceed its cohesion due to the thermal shock produced by laser.The quality of the Al2O3 layer of the film stacks is improved by using buffer layer of SiO2 or MgF2,therefore strengthen the performance of the laser-induced damage of the coating.