| 摘要 |
The invention provides a method of modifying a planar waveguide core formed on a planar substrate and having at least one rough sidewall. The method comprises the steps of forming an overlayer having substantially the same refractive index as the waveguide core over each rough sidewall of the waveguide core so as to smooth over the sidewall roughness; and etching back the overlayer to form a desired waveguide structure with reduced sidewall roughness, wherein the rough sidewalls of the original waveguide core remain substantially coated with overlayer material in the desired waveguide structure. The roughness of the original sidewalls of the waveguide core is effectively reduced by leaving their coated with the overlayer material, which has been etched back. This leaves smoother sidewalls in the desired waveguide structure when compared with the original sidewalls of the waveguide core. The invention is particularly useful for reducing sidewall scattering losses in planar waveguide optical amplifiers.
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