亚波长光栅偏振片的纳秒脉冲激光损伤特性

偏振片在诸多光学系统中有着重要的应用。亚波长介质光栅可用作正入射偏振片，在高能激光系统中有着广泛的应用前景。为了探究波长为1 064 nm的纳秒脉冲激光对于亚波长全介质光栅的诱导损伤特性，使用了粒子群优化算法结合严格耦合波分析设计了光栅的几何参数，计算表明亚波长光栅偏振片在入射光波长1 064 nm附近带宽0.5 nm内，平均消光比为1 500。使用了紫外曝光配合离子束刻蚀的工艺制备了HfO₂光栅，并对其纳秒脉冲激光损伤阈值进行了测试。测试结果表明S光损伤阈值约为P光损伤阈值的5倍，且都大于5 J/cm2。结果表明亚波长全介质光栅偏振片可广泛用于正入射激光系统中。

Nanosecond pulse laser damage characteristics of sub-wavelength gratings polarizers

Polarizers are important components for many optical systems. Sub-wavelength dielectric gratings can be used as polarizers under normal incidence, and these have broad application prospects in high-energy laser systems. In order to investigate the induced damage characteristics of nanosecond pulse laser with wavelength of 1 064 nm for subwavelength all dielectric gratings, the particle swarm optimization algorithm was used to design the geometric parameters of the grating with rigorous coupled wave analysis. The calculation results show that the subwavelength grating polarizer has 0.5 nm bandwidth and a theoretical extinction ratio of 1 500 at wavelength of 1 064 nm. This grating was fabricated by ultraviolet(UV) exposure and ion beam etching, and its nanosecond pulsed laser damage threshold was tested. The test results show that the laser induced damage threshold of S polarized light is about 5 times of that of P polarized light, and all of them are greater than 5 J/cm2. The results indicate that the sub-wavelength all dielectric grating polarizers can be widely used in laser system under normal incidence.