Broadband high reflectivity in subwavelength-grating slab waveguides

TL;DR

This paper demonstrates that subwavelength dielectric grating slab waveguides can achieve ultra-broadband high reflectivity by leveraging mode interference, with potential applications in optical devices requiring wide-angle and broadband performance.

Contribution

It introduces a novel design of subwavelength grating slab waveguides that attain ultra-broadband high reflectivity through mode coupling and interference effects.

Findings

Reflectivity R > 0.99 over >30% bandwidth

Incident-angle R > 0.99 extends over >40 degrees

Design achieves interference among multiple guided modes

Abstract

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