Zhang Lei, Huang Li, Fan Sijun, Bai Gongxun, Li Kefeng, Chen Wei, Hu Lili
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China.
Appl Opt. 2010 Dec 10;49(35):6668-74. doi: 10.1364/AO.49.006668.
We simulate and calculate numerically the electromagnetic field and energy flux around a surface crack of an Nd-doped phosphate laser glass by using the finite-difference time-domain method. Because of a strong interference between the incident wave and the total internal reflections from the crack and the glass surface, the electric field is redistributed and enhanced. The results show that the electric-field distribution and corresponding energy flux component depend sensitively on the light polarization and crack geometry, such as orientation and depth. The polarization of the incident laser beam relative to the crack surfaces will determine the profile of the electric field around the crack. Under TE wave incidence, the energy flux peak is always inside the glass. But under TM wave incidence, the energy flux peak will be located inside the glass or inside the air gap. For both incident modes, the light intensification factor increases with the crack depth, especially for energy flux along the surface. Because cracks on the polished surfaces are the same as the roots extending down, the probability for much larger intensification occurring is high. The results suggest that the surface laser-damage threshold of Nd-doped phosphate may decrease dramatically with subsurface damage.
我们采用时域有限差分法对掺钕磷酸盐激光玻璃表面裂纹周围的电磁场和能流进行了数值模拟和计算。由于入射波与裂纹和玻璃表面的全内反射之间存在强烈干涉，电场会重新分布并增强。结果表明，电场分布和相应的能流分量敏感地取决于光的偏振和裂纹几何形状，如取向和深度。入射激光束相对于裂纹表面的偏振将决定裂纹周围电场的分布。在TE波入射下，能流峰值总是在玻璃内部。但在TM波入射下，能流峰值将位于玻璃内部或气隙内部。对于两种入射模式，光增强因子都随裂纹深度增加，特别是沿表面的能流。由于抛光表面上的裂纹与向下延伸的根部相同，发生更大增强的可能性很高。结果表明，掺钕磷酸盐的表面激光损伤阈值可能会因亚表面损伤而显著降低。
