Polarization-independent light-dispersing device based on diffractive optics

Abstract

We report a light-dispersing device comprised of two transmission gratings and a wave plate. The gratings split the light incident at the Bragg angle into two orthogonally polarized components. The wave plate, which is placed between the gratings, functions as a polarization converter for oblique illumination. Appropriate assembly of these optical parts results in efficient diffraction of the unpolarized light with high spectral resolution. Using coupled-wave theories and Mueller matrix analysis, we constructed a device with a grating period of 400 nm for the spectral range of 680 ± 50 nm. We verified the proposed polarization-independent light-dispersing concept from the evaluation of this device.