Reflection-enhanced photo-detector

A system, comprising:

• a processor;
• a memory storing a program module that is configured to be executed by the processor;
• and
• an optical device, wherein the optical device includes:
• an optical waveguide configured to convey an optical signal having a wavelength;
• a photo-detector having a first end and a second end on opposite sides of side surfaces of the photo-detector, wherein a bottom surface of the photo-detector is disposed on and optically coupled to a region of a top surface of the optical waveguide, wherein the photo-detector is configured to convert the optical signal to an electrical signal;
• and
• a mirror after and proximate to the second end of the photo-detector, wherein the mirror is in a plane of the optical waveguide, and
• wherein the mirror is coupled to an end of the optical waveguide on a side surface of the optical waveguide, wherein the end of the optical waveguide is aligned with the second end of the photo-detector, wherein the mirror is configured to reflect the optical signal back toward the optical waveguide, wherein the mirror causes the optical signal to move in a reversed direction, thereby increasing an absorption length of the photo-detector, and wherein the optical signal is evanescently coupled between the optical waveguide and the photo-detector.

A method for converting an optical signal into an electrical signal, wherein the method comprises:

• conveying the optical signal in an optical waveguide in a first propagation direction;
• evanescently coupling the optical signal into a photo-detector disposed on a surface of the optical waveguide;
• converting a portion of the optical signal into an electrical signal in the photo-detector;
• reflecting a remainder of the optical signal back toward the optical waveguide in a second propagation direction using a mirror proximate to an end of the photo-detector and in a plane of the optical waveguide, wherein the mirror causes the optical signal to move in a reversed direction, thereby increasing an absorption length of the photo-detector;
• evanescently coupling the remainder of the optical signal into the photo-detector;
• and
• converting a portion of the remainder of the optical signal into the electrical signal in the photo-detector,
• wherein a bottom surface of the photo-detector is disposed on and optically coupled to a region of a top surface of the optical waveguide, wherein the mirror is coupled to an end of the optical waveguide on a side surface of the optical waveguide, wherein the end of the optical waveguide is aligned with the end of the photo-detector on a side surface of the photo-detector.