Superconformal recessed feature fill sol-gels

A method of producing a superconformal optical coating, the method comprising:

• providing a feature fill sol-gel material, wherein forming the feature fill sol-gel material comprises dissolving or suspending a first titanium precursor comprising Titanium(IV) and an inorganic ligand in a solvent;
• applying the feature fill sol-gel material onto a substrate comprising a plurality of recessed features;
• and
• annealing the feature fill sol-gel material at an annealing temperature less than 500° C. to form the superconformal optical coating, wherein:
• the feature fill sol-gel material fully densifies at the annealing temperature;
• and
• the superconformal optical coating fills the plurality of recessed features without forming voids.

A waveguide, wherein the waveguide comprises:

• a substrate, wherein the substrate comprises a plurality of recessed features extending from an outer surface of the substrate to a depth into a bulk of the substrate;
• and
• a superconformal optical coating applied to the substrate, wherein the superconformal optical coating:
• is formed from a feature fill sol-gel material comprising a titanium precursor having an oxo-ligand;
• and
• fills the plurality of recessed features, after annealing, without forming voids.