Enhancement of the Efficiency Based on a Sandwiched Grating for Separating Polarized Beams

We describe a novel polarizing beam splitter (PBS) based on a sandwiched grating, where a binary grating is covered by a layer. A modal method is employed to optimize the grating period with the duty cycle of 0.5 by the excited modes in the grating region. The grating depth and thickness of the covering layer are accurately optimized using a rigorous coupled-wave analysis by the numerical calculation. The sandwiched PBS grating can show high efficiency for both transverse electric polarization in the -1st order and transverse magnetic polarization in the zeroth order. The significant wide fabrication tolerances are given for mass production during fabrication.