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 LambHa900 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 SiO_2 and MgF_2 and that of the coating with buffer layer of Al_2O_3 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 Al_2O_3 layer of the film stacks is improved by using buffer layer of SiO_2 or MgF_2, therefore strengthen the performance of the laser-induced damage of the coating.