Patent ID: 8031991

Claim:
A silicon-based optical coupler for providing optical coupling between a free space optical signal exhibiting a large mode field diameter and a single mode optical waveguide formed on an optical substrate and exhibiting a mode field diameter smaller than the optical signal, the silicon-based optical coupler comprising: an antiresonant reflecting optical waveguide (ARROW) structure disposed at an endface of the optical substrate and comprising a low index core region and a high index reflective boundary layer having a refractive index higher than the low index core region, the arrow structure exhibiting a large mode field diameter to provide coupling for the free space optical signal, the high index reflective boundary layer disposed under the low index core region forming in combination a resonant cavity; and a nanotaper coupling waveguide including a core region having a greater refractive index than the low index core region of the ARROW structure, the nanotaper coupling waveguide disposed between the ARROW structure and the single mode optical waveguide for providing coupling therebetween, the nanotaper coupling waveguide includes a narrow tip termination, tapering outwardly therefrom to an endface, the single mode waveguide coupled to the endface of the core region of the nanotaper coupling waveguide, wherein the nanotaper coupling waveguide performs mode field diameter conversion between the large mode field diameter ARROW structure and the small mode field diameter single mode optical waveguide.