Zhang Jinlong, Bu Xiaoqing, Jiao Hongfei, Ma Bin, Cheng Xinbin, Wang Zhangshan
Opt Express. 2017 Jan 9;25(1):305-312. doi: 10.1364/OE.25.000305.
Broadband low dispersion (BBLD) mirrors are an essential component in femto-second (fs) pulse laser systems. We designed and produced TaO-HfO/SiO composite quarter-wave and non-quarter-wave HfO/SiO BBLD mirrors for the 30fs petawatt laser system. The laser damage properties of the BBLD mirrors were investigated in an uncompressed sub-nanosecond laser pulse. It showed that the TaO-HfO/SiO composite BBLD mirror possessed higher LIDT due to the low electric-field intensity (EFI) in the case of the coating without artificial nodules. Nevertheless, the LIDT of the composite mirror was significantly lower than the non-quarter-wave HfO/SiO mirror when the nodules exist. The EFI simulation and damage morphology of the nodules analysis demonstrated that the nodule leading to the light intensification in the middle of the boundary between the nodular and the surrounding coating, thus the outermost HfO/SiO layers cannot protect the TaO/SiO layers, and resulting to the significantly low LIDT. This study shed some light on the development of high-laser-damage BBLD mirrors for pulse compression laser systems.
宽带低色散（BBLD）镜是飞秒（fs）脉冲激光系统的重要组成部分。我们为30fs拍瓦激光系统设计并制作了TaO-HfO/SiO复合四分之一波和非四分之一波HfO/SiO BBLD镜。在未压缩的亚纳秒激光脉冲中研究了BBLD镜的激光损伤特性。结果表明，在无人工结节的涂层情况下，由于电场强度（EFI）较低，TaO-HfO/SiO复合BBLD镜具有较高的激光诱导损伤阈值（LIDT）。然而，当存在结节时，复合镜的LIDT显著低于非四分之一波HfO/SiO镜。结节的EFI模拟和损伤形态分析表明，结节导致结节与周围涂层边界中间的光强增强，因此最外层的HfO/SiO层无法保护TaO/SiO层，从而导致LIDT显著降低。这项研究为脉冲压缩激光系统的高激光损伤BBLD镜的发展提供了一些启示。
