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Abstract

In a planar lightwave circuit, a method of making an optical waveguide that resists core deformation. The method includes a step of forming a core layer on a bottom clad. A waveguide core is formed from the core layer using an etching process. The waveguide core is fabricated to have a higher refractive index than the bottom clad. A silica glass cap layer is then formed over the waveguide core and the bottom clad. A top clad is then formed over the waveguide core, the silica glass cap layer, and the bottom clad. The waveguide core has a higher refractive index than the top clad. The silica glass cap layer maintains the shape of the waveguide core during an anneal process of the top clad. The silica glass cap layer can be deposited using PECVD (plasma enhanced chemical vapor deposition). The silica glass cap layer can be between 0.3 to 2 microns thick. The silica glass cap layer can be undoped silica glass. The silica glass cap layer can have a higher reflow temperature than the waveguide core to prevent deformation of the waveguide core. The silica glass cap layer also can prevent diffusion of dopant between the waveguide core and the top clad.

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First Claim