Simply structured polarization-independent high efficiency multilayer dielectric gratings

A polarization-independent multilayer dielectric diffraction grating with a low aspect ratio and high diffraction efficiency was designed and fabricated. The diffraction grating designed with a grating density of 1200 lines/mm had an aspect ratio of 0.59, mean polarization-independent diffraction efficiency in the Littrow angle of ±2.5^∘, and 1030-1080 nm wavelength range of 97.2%. The designed grating was fabricated using ion assisted deposition and reactive ion etching techniques. The mean polarization-independent diffraction efficiency of the fabricated grating was 96.1%, and its standard deviation was 0.68%. The fabricated diffraction grating was irradiated with a 1064 nm cw laser, with a power density of 30kW/cm², for 1 min to measure the temperature change before and after the laser application. It was verified that the temperature variation of the diffraction grating without heat treatment was 8.8°C, and the temperature variation after heat treatment at 400°C decreased to 2.3°C.