Inverted 45° mirror for photonic integrated circuits

A method of forming a mirror in a photonic integrated circuit (PIC), the method comprising:

• performing an etch of a crystalline semiconductor substrate to form a facet oriented 45° from a top surface of the substrate;
• bonding the top surface of the substrate to a handle wafer;
• and
• forming, in the substrate, an optical waveguide that is optically coupled with the facet.

A mobile computing platform comprising:

• a processor;
• a memory;
• a display;
• and
• an photonic integrated circuit (PIC) chip comprising
• a {100} crystalline device layer disposed over a substrate,
• a thin film dielectric layer disposed over the {110} crystal plane, and
• an optical waveguide formed in the device layer, wherein the {110} crystal plane of the device layer forms an end facet optically coupled to the optical waveguide and oriented 45° with respect to a top surface of the substrate, and further wherein the device layer with the end facet and portions of the device layer opposite the end facet being in direct contact with the optical waveguide form a bridge over a void located over the substrate and beneath the dielectric layer.