Modification of planar waveguide facet reflectivity with subwavelength gratings

The functionality and performance of many planar waveguide devices, including lasers and optical amplifiers, are critically affected by the reflectivity of the waveguide facets. For high index contrast waveguide devices, the Fresnel reflection at the facet is a significant contribution to the fibre-to-chip coupling loss and the return loss. Currently, the common method to control the facet reflectivity of planar waveguides is the deposition of anti-or high-reflective coatings.