基于共焦成像法的亚表层损伤散射仿真

Simulation of sub-surface damage scattering based on confocal imaging

光学零件的亚表面缺陷直接影响其使用性能和抗激光损伤阈值等重要指标,而造成这些危害的根本原因是由损伤层引入的入射光的散射。采用时域有限差分(FDTD)法,结合共焦层析测量系统进行模拟仿真。首先,针对常见的光学材料,分析了入射光经由亚表层中的微裂纹、气泡等常见缺陷调制后的光场分布,并结合不同形态参数和光学参数建立模型;其次,引入球面波激励源,模拟计算了入射波聚焦点沿固定间隔逐渐偏离缺陷时的散射分布。结果表明:共焦层析测量系统能够实现对亚表层损伤的测量,满足纵向响应函数趋势。

The sub-surface damage of the optical elements directly affects their performance, stability, resistance to laser damage threshold and durability, and the fundamental cause is the scattering of the defected layer to the inception light. With FDTD method, and the laboratory laser scanning confocal microscopic measurement system, simulation was conducted to analyze the scattering characters of optical elements of sub-surface. Firstly, for common optical materials, the optical field distribution of inception light after being modulated by common defects like the microcracks and bubbles was simulated, and simulation models were built with combination of various morphological and optical parameters. Secondly, the spherical wave excitation source was adopted in the resultant field area, and simulated calculation was conducted when the incident wave focus along the fixed interval departed from the defect of the scattering distribution and detector received signal strength. The result of the simulation showed that, laser scanning confocal microscopic measurement system could realize the measurement of the sub-surface damages and meet the trend of vertical response functions.