Patent ID: 8358889

Claim:
A method for fabricating a planar lightwave circuit (PLC) device, the method comprising: selectively doping an area of a core layer with a dopant to define a core area of a waveguide; preparing Bragg grating corrugations on top of the core area across a predefined width of the waveguide; forming a barrier layer on top of the Bragg grating corrugations, wherein a material of the barrier layer is selected to prevent outdiffusion of the dopant into the barrier layer; lithographically patterning a top surface of the PLC device to cover the Bragg grating corrugations underneath during subsequent etching; etching through the barrier layer and through the core layer to expose waveguide sidewalls; encompassing the core area at least partially with a cladding material; and annealing the PLC device at a high temperature, allowing outdiffusion of the dopant from the core area into the cladding material, thereby smoothening the waveguide sidewalls.