摘要
用波长1.06μm、半高宽10ns的脉冲Nd:YAG激光辐照铜膜镜面,在激光辐照区,用光学显微镜观察到有规律的环形波纹状损伤图案,波纹平均周期约几十μm。通过对光路系统分析,认为样品前的小孔光阑对激光产生了菲涅尔衍射,使得在样品表面光强分布变成周期性环状分布。在极短的相互作用时间内,热扩散很小,损伤图案依赖于光强分布。并依据实验参数,用柯林斯公式对样品表面的光强分布进行了计算,所得光强分布的周期与损伤波纹的周期基本一致。
The damaged spot of copper film mirror irradiated by pulsed Nd:YAG laser is analyzed using an optical microscope. The periodic damage ring is found at the laser irradiation spot, the average spacing of these rings is about 45μm. The damage ring can be observed obviously only in the periphery of the laser spot under lower laser energy density; as laser fluence increases, the periodic damage rings cover the whole laser spot; under higher laser energy density, the whole film is damaged and the rings disappear. A Fresnel diffraction model is used to explain the appearance of these rings. The laser beam is diffracted by the aperture in the optic path, laser intensity distribution at the copper film mirror becomes periodic rings and damage ripple pattern forms instantly with the laser ablation and evaporation. The laser intensity distribution at the mirror surface is calculated using Collins formula, with which the period of damage rings and other phenomena can be explained.
出处
《强激光与粒子束》
EI
CAS
CSCD
北大核心
2003年第3期225-228,共4页
High Power Laser and Particle Beams
基金
中国工程物理研究院基金资助课题(20020424)
国家863计划项目资助课题
