Photonic device and method of making same

A system comprising:

• an optical fiber configured to carry an optical signal;
• and
• a photonic device in optical communication with the optical fiber, wherein the photonic device comprises:
• a device region;
• a silicon layer, wherein the silicon layer includes a grating and a waveguide portion, wherein the grating is configured to optically couple the waveguide portion to the optical fiber;
• a cladding layer over the waveguide portion, wherein the device region is free of the cladding layer;
• a low refractive index layer in direct contact with the cladding over the waveguide portion, wherein a refractive index of the low refractive index layer is less than a refractive index of silicon nitride, and the low refractive index layer comprises silicon oxide, silicon carbide, silicon oxynitride, silicon carbon oxynitride, aluminum oxide or hafnium oxide;
• and
• an interconnect structure over the low refractive index layer.

A photonic device comprising:

• a silicon layer, wherein the silicon layer extends from a waveguide region of the photonic device to a device region of the photonic device, the silicon layer includes a waveguide portion in the waveguide region, and the silicon layer includes a grating for optically coupling an incident beam with the waveguide portion;
• a cladding layer over the waveguide portion, wherein the device region is free of the cladding layer;
• a low refractive index layer in direct contact with the cladding layer, wherein the low refractive index layer comprises silicon oxide, silicon carbide, silicon oxynitride, silicon carbon oxynitride, aluminum oxide or hafnium oxide;
• and
• an interconnect structure over the low refractive index layer.