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.