Waveguide transitions for hybrid thin-silicon/III-V photonics

A method of manufacturing a photonic device, the method comprising:

• providing a substrate comprising a lower silicon layer disposed on an insulating layer, the substrate comprising a first section, second section, and third section arranged sequentially along an optical axis of the photonic device;
• forming an upper silicon layer over the lower silicon layer in the first and second sections with a lower dielectric layer separating the upper and lower silicon layers;
• patterning the upper silicon layer to form:
• a first upper waveguide segment in the first section, the first upper waveguide segment increasing in width from a first width to a second width at an interface between the first and second sections;
• and
• a second upper waveguide segment in the second section, the second upper waveguide segment decreasing in width from the second width at the interface between the first and second sections to a third width at an interface between the second and third sections;
• patterning the lower silicon layer to form:
• a first lower waveguide segment in the second section decreasing in width from a fifth width at the interface between the first and second sections to a fourth width at the interface between the second and third sections, the fifth width being greater than the second width, the fourth width being greater than the third width;
• and
• a second lower waveguide segment in the third section having the fourth width, formed in the lower silicon layer contiguously with the first lower waveguide segment;
• forming a top dielectric layer above the upper silicon layer;
• bonding a III-V semiconductor structure to the top dielectric layer in the first section;
• and
• patterning the III-V semiconductor structure to form a III-V waveguide overlapping the first upper waveguide segment in the first section.