Multiple-core planar optical waveguides and methods of fabrication and use thereof

Abstract From the Canadian patent

A multiple-core optical waveguide comprises: a substrate; lower and upper waveguide core layers; a waveguide core between the upper and lower waveguide core layers; upper and lower cladding; and middle cladding between the upper and lower waveguide core layers substantially surrounding the waveguide core. Each of the lower, middle, and upper claddings has a refractive index less than refractive indices of the lower waveguide core layer the upper waveguide , core layer, and the waveguide core. Along at least a given portion of the optical waveguide, the upper and lower waveguide core layers extend bilaterally substantially beyond the lateral extent of a propagating optical mode …