Patent ID: 7058261

Claim:
An arrangement for providing optical coupling between a multi-wavelength optical signal and a relatively thin, planar silicon optical waveguide, the arrangement comprising a prism coupling structure disposed over the evanescent coupling layer, the prism coupling structure including at least one coupling facet oriented at a predetermined angle with respect to the waveguide surface for intercepting optical signals within a defined wavelength range and a prism coupling surface disposed above and essentially parallel to the upper surface of the relatively thin, planar optical waveguide for coupling the multi-wavelength optical signal into the relatively thin, planar optical waveguide; and a grating structure disposed between the prism coupling surface and the planar silicon optical waveguide, the grating structure having a predetermined grating period (Λ) less than the wavelength (λ) of the multi-wavelength optical signal and a predetermined height (h) so as to transmit substantially in the zeroth order diffraction mode over the defined wavelength range and produce a predetermined effective refractive index profile in at least the region along the prism coupling surface that increases optical coupling efficiency over the defined wavelength range, wherein at least one of the period and duty cycle of the grating changes in value along a longitudinal axis thereof so as to create an effective refractive index profile varies monotonically about an optimum effective refractive index value associated with a center wavelength of the defined wavelength range.