US Patent 11906781 End-face coupling structures underneath a photonic layer

A method includes providing a photonic wafer that includes an electrical layer and a layer disposed on a substrate. The layer includes at least one optical waveguide that is disposed between the electrical layer and the substrate. The method also includes removing a portion of the substrate underneath the at least one optical waveguide and forming an end-face coupler. A portion of the end-face coupler is within the removed portion of the substrate. The end-face coupler transmits an optical signal to, or receives an optical signal from, an external optical device.