Reflection-enhanced photo-detector

Patent metadata

Field	Value
Publication number	US-10119857-B2
Application number	US-201213588248-A
Country	US
Kind code	B2
Filing date	Aug 17, 2012
Priority date	Aug 17, 2012
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

An integrated optical device includes a photo-detector (such as germanium) optically coupled to an optical waveguide. This photo-detector is deposited on the optical waveguide, and an optical signal propagating in the optical waveguide may be evanescently coupled to the photo-detector. In order to increase the absorption length of the photo-detector, a mirror (such as a distributed Bragg reflection grating) is included in the optical waveguide near the end of the photo-detector. This mirror reflects the optical signal back toward the photo-detector, thereby increasing the absorption of the optical signal by the photo-detector. In addition, absorption may be reduced by using electrical contacts that are electrically coupled to the photo-detector at locations where the optical mode of the optical signal is largely in the underlying optical waveguide, and by using a fingered metal layer to couple to the electrical contacts.

First claim

What is claimed is:

1. An optical device, comprising:
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.

2. The optical device of claim 1 , wherein the mirror is included in the optical waveguide.

3. The optical device of claim 1 , wherein the mirror includes an element selected from the group consisting of: a distributed Bragg reflection grating and an etched vertical facet with a reflection coating.

4. The optical device of claim 1 , wherein the photo-detector includes periodic rows of electrical contacts along a length of the photo-detector.

5. The optical device of claim 4 , wherein the electrical contacts are positioned at locations along the length where the optical signal is substantially in the optical waveguide.

6. The optical device of claim 4 , wherein electrical contacts in a given row are electrically connected to each other via a metal layer.

7. The optical device of claim 6 , wherein the metal layer is fingered proximate to the electrical contacts.

8. The optical device of claim 1 , wherein the optical waveguide includes a taper that expands a width of the optical waveguide prior to the photo-detector.

9. The optical device of claim 1 , further comprising:
a substrate;
a buried-oxide layer disposed on the substrate; and
a semiconductor layer disposed on the buried-oxide layer, wherein the optical waveguide is included in the semiconductor layer.

10. The optical device of claim 9 , wherein the substrate includes a semiconductor.

11. The optical device of claim 1 , wherein the photo-detector includes germanium.

12. 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.

13. The system of claim 12 , wherein the mirror is included in the optical waveguide.

14. The system of claim 12 , wherein the photo-detector includes periodic rows of electrical contacts along a length of the photo-detector.

15. The system of claim 14 , wherein electrical contacts in a given row are electrically connected to each other via a metal layer.

16. The system of claim 15 , wherein the metal layer is fingered proximate to the electrical contacts.

17. The system of claim 14 , wherein the electrical contacts are positioned at locations along the length where the optical signal is substantially in the optical waveguide.

18. 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.

Assignees

• Li Guoliang
• Zheng Xuezhe
• Luo Ying L
• Krishnamoorthy Ashok V
• Oracle Int Corp

Inventors

• Li Guoliang
• Zheng Xuezhe
• Luo Ying L
• Krishnamoorthy Ashok V

Classifications

• G01J1/42

  using electric radiation detectors (optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10) · CPC title

• G01J1/0407 Primary

  Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings · CPC title

• G01J1/0425

  using optical fibers · CPC title

• G02B6/12004

  Combinations of two or more optical elements · CPC title

• G01J1/0209

  Monolithic · CPC title