Optical device with substrate and index-matched coupler field

Abstract

Examples are disclosed that relate to forming gratings on waveguides. One example provides a method of fabricating an optical grating. The method comprises applying a precursor solution onto a substrate, the precursor solution comprising a metal-ligand complex, to form a precursor solution film, and removing at least some solvent from the precursor solution film to form a metal oxy-hydroxy with a first refractive index. The method further comprises forming a patterned mask layer on the metal oxy-hydroxy film, and transferring a pattern of the patterned mask layer to the metal oxy-hydroxy film by dry etching to form a patterned metal oxy-hydroxy film. The method further comprises exposing the patterned metal oxy-hydroxy film to one or more of ultraviolet light or heat to form a patterned metal oxide film with a second refractive index that is closer to a refractive index of the substrate than the first refractive index.

Dependencies are inferred from the claim text.