针对强激光系统中常用的1 053 nm激光器进行了偏振光栅结构的优化设计。利用严格耦合波理论分析了光栅偏振器的衍射特性及消光比, 分析显示偏振光栅周期为600 nm, 占宽比为0.535~0.55, 槽形深度为1 395 nm~1 420 nm时, 可保证其在1 053 nm波长下, 透射率高于95%, 消光比大于1 500。基于分析结果, 利用全息光刻技术制作了高质量光刻胶光栅掩模, 并采用倾斜转动的离子束刻蚀结合反应离子束刻蚀的方法对该光刻胶光栅掩模进行图形转移, 制作了底部占宽比为0.54, 槽形深度为1 400 nm的光栅偏振器。实验测量显示其透射率为92.9%, 消光比达到160。与其他制作光栅偏振器方法相比, 采用单光刻胶光栅掩模结合倾斜转动的离子束刻蚀工艺, 不但简化了制作工艺, 而且具有激光损伤阈值高、成本低的优点。由于该技术可制作大面积光栅, 特别利于在强激光系统中应用。

The structure of a grating polarizer in common 1053 nm lasers was optimized for high power laser systems. The diffraction characteristics and extinction ratio of the grating polarizer were investigated by using rigorous coupled-wave theory. The results show when the grating period, duty cycle and the groove depth of the grating are 600 nm, 0.535-0.55 and 1 395-1 420 nm at a wavelength of 1053 nm, respectively, the extinction ratio could be more than 1500, and the optical transmittance of the TM-polarized wave could be over 95%. Based on the above analysis, a high quality photoresist grating mask was made by holographic lithography. Then, it was transferred to the fused silica substrate by tilted rotating ion beam etching and reactive ion beam etching to fabricate a grating polarizer with the period of 600 nm, bottom duty cycle of 0.54 and the groove depth 1 400 nm. Experimental measurements on the grating polarizer show that the optical transmittance is 92.9% and the extinction ratio is 160. Compared with other fabricating methods for the grating polarizer, the proposed method only requires a single layer of photoresist grating mask, which simplifies the fabricating process, enjoys low costs and guarantees the high damage threshold of the grating. As the method can fabricate large scale gratings, it is suitable for applications to the high power laser systems.