Patent ID: 7013067

Claim:
An arrangement for providing optical coupling between a free-space propagating optical signal and an ultrathin silicon waveguide formed in an upper silicon layer of a silicon-on-insulator (SOI) structure, the SOI structure further comprising: a silicon nanotaper structure formed in the upper silicon layer (SOI layer) of the SOI structure, the silicon nanotaper having a first, narrow endface and a second, larger endface with a laterally extending tapered structure therebetween, the second, larger endface coupled to the ultrathin silicon waveguide to provide optical coupling therebetween; a dielectric waveguide coupling layer having a top major surface, with a refractive index greater than the index of the dielectric insulating layer but less than the refractive index of silicon, disposed so as to overly a portion of the dielectric insulating layer in a region where an associated portion of the SOI layer has been removed and optical coupling into the remaining portion of the SOI layer is desired, with an end portion of the dielectric waveguide coupling layer overlapping an end section of the silicon nanotaper including the first, narrow endface to form a mode conversion region between the free-space propagating optical signal and the ultrathin silicon waveguide; and a free-space optical coupling arrangement disposed over the top major surface of the dielectric waveguide coupling layer so as to couple the propagating optical signal between free space and the dielectric waveguide coupling layer and thereafter into the ultrathin silicon waveguide.