A method comprising: forming a first waveguide (235, 610) in an insulation layer (110, 315, 330, 755) of an optical device; after forming the first waveguide, disposing a crystalline, semiconductor layer (205, 310A, 760) on the insulation layer, wherein forming the first waveguide further comprises: forming in the insulation layer a waveguide adapter (410, 1200) which abuts an external coupling surface of the optical device, the waveguide adapter enabling the optical device to couple to an external light source to receive or transmit optical energy; and forming a second waveguide (220, 605) in the semiconductor layer, wherein the second waveguide at least partially overlaps the first waveguide in the insulation layer, characterized in that the waveguide adapter (410, 1200) comprises a first prong (415A, 1205A) and a plurality of second prongs (415B-D, 1205B-E), wherein the first prong and second prongs are configured to at least one of receive and transmit optical energy via the coupling surface, wherein a dimension of the second prongs reduces as the second prongs extend in a direction away from the coupling surface, wherein a dimension of the first prong increases as the first prong extends away from the coupling surface, the dimensions of the first and plurality of second prongs at the coupling surface being chosen such that the mode of the prongs at the coupling interface closely matches the mode of the external light source, the mode gradually transitioning to a mode predominantly confined in the first prong at positions farther away from the coupling surface. forming a first waveguide (235, 610) in an insulation layer (110, 315, 330, 755) of an optical device; after forming the first waveguide, disposing a crystalline, semiconductor layer (205, 310A, 760) on the insulation layer, wherein forming the first waveguide further comprises: forming in the insulation layer a waveguide adapter (410, 1200) which abuts an external coupling surface of the optical device, the waveguide adapter enabling the optical device to couple to an external light source to receive or transmit optical energy; and forming a second waveguide (220, 605) in the semiconductor layer, wherein the second waveguide at least partially overlaps the first waveguide in the insulation layer, forming in the insulation layer a waveguide adapter (410, 1200) which abuts an external coupling surface of the optical device, the waveguide adapter enabling the optical device to couple to an external light source to receive or transmit optical energy; and forming a second waveguide (220, 605) in the semiconductor layer, wherein the second waveguide at least partially overlaps the first waveguide in the insulation layer, characterized in that the waveguide adapter (410, 1200) comprises a first prong (415A, 1205A) and a plurality of second prongs (415B-D, 1205B-E), wherein the first prong and second prongs are configured to at least one of receive and transmit optical energy via the coupling surface, wherein a dimension of the second prongs reduces as the second prongs extend in a direction away from the coupling surface, wherein a dimension of the first prong increases as the first prong extends away from the coupling surface, the dimensions of the first and plurality of second prongs at the coupling surface being chosen such that the mode of the prongs at the coupling interface closely matches the mode of the external light source, the mode gradually transitioning to a mode predominantly confined in the first prong at positions farther away from the coupling surface.