Patent ID: 7646957

Claim:
A method comprising: (i) propagating an optical signal along an optical waveguide as an optical mode supported by the optical waveguide; and (ii) transferring the optical signal between the optical waveguide and another optical waveguide or device, wherein the optical waveguide comprises: (a) a substantially planar waveguide substrate; (b) a lower waveguide core layer; (c) an upper waveguide core layer; (d) a waveguide core between the upper and lower waveguide core layers; (e) lower cladding between the substrate and the lower waveguide core layer; (f) upper cladding above the upper waveguide core layer; and (g) middle cladding between the upper and lower waveguide core layers substantially surrounding the waveguide core, and wherein: (1) the lower cladding has a refractive index less than refractive indices of the lower waveguide core layer, the upper waveguide core layer, and the waveguide core; (2) the middle cladding has a refractive index less than refractive indices of the lower waveguide core layer, the upper waveguide core layer, and the waveguide core; (3) the upper cladding has a refractive index less than refractive indices of the lower waveguide core layer, the upper waveguide core layer, and the waveguide core; (4) a width of the waveguide core is substantially larger than a thickness thereof; (5) an upper surface of the waveguide core is substantially flat; (6) the upper and lower waveguide core layers and the waveguide core are arranged so as to together support the optical mode; (7) the upper and lower waveguide core layers extend bilaterally substantially beyond the lateral extent of the supported optical mode; and (8) the upper and lower waveguide core layers and the waveguide core are arranged so that the supported optical mode is substantially confined bilaterally by the waveguide core, from below by the lower waveguide core layer, and from above by the upper waveguide core layer.