关键词: 熔石英/
CO2激光损伤修复/
光场调制/
标量衍射理论
English Abstract
Study of downstream light intensity modulation induced by mitigated damage pits of fused silica using numerical simulation and experimental measurements
Bai Yang1 2,Zhang Li-Juan1,
Liao Wei1,
Zhou Hai1,
Zhang Chuan-Chao1,
Chen Jing1,
Ye Ya-Yun1,
Jiang Yi-Lan1,
Wang Hai-Jun1,
Luan Xiao-Yu1,
Yuan Xiao-Dong1,
Zheng Wan-Guo1
1.Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;
2.Graduate School of China Academy of Engneering Physics, Beijing 100088, China
Fund Project:Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 11404301).Received Date:24 August 2015
Accepted Date:16 September 2015
Published Online:20 January 2016
Abstract:For high-power UV laser facilities, one of the key problems limiting the maximum light influence and safe routine operation is that the UV laser induces damage to fused silica optics. The most effective mitigation protocol of the damaged optics is the CO2 laser processing that leads to make locally melt or evaporate the damage. While the mitigated damage sites possess particular morphology, which may modulate the passing laser beam and induce the downstream intensification that will ruin the neighbor optics. In this work, the morphology features of the mitigated damage pits of fused silica optics are systematically investigated. According to the measured morphology features, a 3D grid model of mitigated pit is built, and the downstream light intensity distribution of the mitigated pit model under incident 351 nm laser is studied by scalar diffraction theory and fast fourier transform (FFT) methods. Results indicate that there are two kinds of downstream intensification: off-axis and on-axis intensifications. In the former intensification, the maximum intensity is located near the output surface of the optics and comes mainly from the depth of the mitigated pit; it increases with the depth. In the alter intensification, the maximum intensity is located far from the output surface of the optics and is mainly dependent on the height of the rim structure at the fringe of the mitigated damage pit; so it increase with increasing height. In addition, it is found that the location of the maximum off-axis or on-axis intensity can approach the output surface of the optics with increasing maximum intensity. For comparison, experimental measurements of downstream intensification induced by the mitigated pits are carried out, and the experimental results are almost consistent with the numerical simulation, implying the validity of the numerical simulation of the mitigated pit model. Results of this research indicate that the downstream intensification of mitigated pits can be suppressed by controlling the morphology features of mitigated pits. this is significant for the development and improvement of the mitigated techniques of damage optics.
Keywords: fused silica/
CO2 laser mitigation/
modulation/
scalar diffraction theory
