Patent ID: 8900899

Claim:
A method for producing a high-refractive index contrast and low loss optical waveguide, the method comprising the steps of: depositing a lower cladding material layer with a first low refractive index on a silicon base substrate; depositing or growing a refractory metal layer on top of the lower cladding material layer with the first low refractive index; forming a trench in a top diffusion barrier layer deposited on the refractory metal layer, wherein the trench has an open surface for the refractory metal layer; oxidizing the open surface of the trench to high-temperature ambient oxygen, wherein the open surface subsequently forms an oxidized refractory metal region, and wherein other parts of the refractory metal layer still covered under the top diffusion layer remain unchanged as a non-oxidized refractory metal region; removing the top diffusion barrier layer using one or more chemical etching agents; removing the non-oxidized refractory metal region by using a dry-etching tool with high-etch selectivity to preserve the oxidized refractory metal region; and depositing a top cladding layer made of a second low refractive index material to encapsulate the oxidized refractory metal region on top of the lower cladding material layer.