Patent ID: 8078020

Claim:
An apparatus, comprising: an optical-mode-converter structure, including: a tapered optical core on a planar substrate; an optical cladding layer covering said tapered optical core; a mode-expanding layer directly contacting said tapered optical core, wherein: said optical cladding layer directly contacts said mode-expanding layer that directly contacts said tapered optical core, said mode-expanding layer has a refractive index that is in-between a refractive index of said tapered optical core and a refractive index of said optical cladding layer, and said mode-expanding layer directly contacting said tapered optical core has a uniform thickness; and a second mode-expanding layer is located in-between said mode-expanding layer and said optical cladding layer, said second mode-expanding layer having a refractive index that is in-between said refractive index of said mode-expanding layer and said refractive index of said optical cladding layer.