Patent ID: 7204932
Filing Date: 2007-04-17
Classification: G02B

Abstract:
1. A method of fabricating a polarisation rotator comprising a substrate, a rib waveguide on a surface of the substrate having a propagation axis and opposite side walls, a recess in one of the side walls of the waveguide to provide an asymmetric waveguide section for imparting polarisation rotation to radiation propagating along the propagation axis, the recess providing a first side surface within the recess, and an etch pit adjacent said one side wall providing a second side surface adjoining the first side surface and tilted relative to the first side surface, the method including the steps of, during formation of the waveguide on the surface of the substrate, etching the etch pit in the substrate surface so as to form the recess in one of the side walls of the waveguide forming the asymmetric waveguide section for imparting polarisation rotation to radiation propagated along the propagation axis, the etching forming the first side surface within the recess, and the side walls of the waveguide being formed by a side wall etching step, wherein the side wall etching step additionally forms the second side surface adjoining the first side surface and tilted relative to the first side surface.