Broadband high reflectivity in subwavelength-grating slab waveguides

摘要

We computationally study a subwavelength dielectric grating structure, showthat slab waveguide modes can be used to obtain broadband high reflectivity,and analyze how slab waveguide modes influence reflection. A structure showinginterference between Fabry-Perot modes, slab waveguide modes, and waveguidearray modes is designed with ultra-broadband high reflectivity. Owing to thecoupling of guided modes, the region with reflectivity R > 0.99 has anultra-high bandwidth ( {\Delta}f/f > 30%). The incident-angle region with R >0.99 extends over a range greater than 40{\deg}. Moreover, an asymmetricwaveguide structure is studied using a semiconductor substrate.