Patent ID: 7391948

Claim:
A waveguide structure comprising: a. a core having a lateral dimension and a vertical dimension and adapted to propagate light along a path defined by the core; and b. a cladding material at least partially surrounding the core, the core and the cladding material each having a refractive index profile in a direction light propagates through the core, wherein at least one of (1) the lateral dimension of the core or (2) the refractive index profile of the core vary along a predefined portion of the core; the refractive index profile of the cladding includes a gradient along the predefined portion and the refractive index profile of the cladding material comprises a refractive index profile for cladding material vertically adjacent to the core; wherein the core comprises a channel waveguide coupled to a taper that laterally flares out from the channel waveguide; the refractive index profile of the core in the region of the channel waveguide is defined by a first refractive index value, n 1 where the taper is coupled to the channel waveguide, where n 1 >n 2 ; and the refractive index profile of the cladding material vertically adjacent to the core is graded from a third refractive index value, n 3 , at the widest point of the taper to a fourth refractive index value, n 4 , where the taper is coupled to the channel waveguide, where n 1 >n 4 , n 2 >n 3 , and n 4 >n 3 .