Numerical analysis of Bragg polarization gratings

Abstract

Here we study Bragg regime polarization gratings (PGs) using an anisotropic rigorous coupled-wave analysis method. We simulate the most important diffraction properties without paraxial approximation, including the angular, spectral, and polarization responses. We first focus on the angular and spectral bandwidths of the transmissive and reflective Bragg PGs optimized for normal incidence. The effects of material birefringence and average index of refraction were investigated. Second, we examine the nonideal Bragg PGs with nonplanar director profiles and identified degradation in optical performance due to the high tilt of the liquid crystal director. Third, we simulate the polarization response of both types of Bragg PGs and observed complicated angular dependence of the polarization output. Qualitatively, good agreement can be observed between the simulation results and prior experimental work. Finally, we fit the measured angular and polarization data to retrieve actual grating parameters and demonstrated excellent quantitative correspondence, which can be particularly useful in closing the gap between design and fabrication.