Optical receiver comprising a receiver photodetector integrated with an imaging array

• US 20050191062A1
• Filed: 10/13/2004
• Published: 09/01/2005
• Est. Priority Date: 10/13/2003
• Status: Active Grant

• Current Assignee: Infrared Newco, Inc.
• Original Assignee: Noble Peak Vision Corp.
• Inventors: Rafferty, Conor S., King, Clifford Alan
• Granted Patent: US 7,643,755 B2
• Time in Patent Office: Days
• US Class Current: 398/202
• CPC Class Codes: H04B 10/118 specially adapted for satellite communication

Abstract

A high-speed optical communications cell is integrated at the interior of a two-dimensional imaging array. The combined receiver and imager carries out both photodetection (converting photons to electrons) and circuit functions (e.g. amplifying and integrating the signals from the photodetectors). The high-speed receiver cell comprises a photodetector and a high-speed amplification circuit, providing an electrical output which can follow a rapidly varying optical signal falling on the photodetector. The imaging array comprises an array of photodetectors and readout circuits, providing an electrical representation of the variation of light with position across the receiver surface. The presence of an imaging array surrounding the communications receiver, and in the same plane as it, allows a single optical path to be used for source acquisition and tracking as well as for data reception

Claims

1. An optical receiver for receiving an optical signal beam from a signal source comprising:

a substrate; and

integrated on the substrate, a) at least one optical receiver cell for receiving the signal beam and converting the optical signal to an electrical signal and b) a plurality of imaging cells to image the signal source for use in aligning the receiver with the source.

2. The receiver of claim 1 wherein the optical receiver cell comprises a high speed photodetector to follow the variation of the optical signal beam.

3. The receiver of claim 2 wherein the optical receiver cell comprises a high speed photodetector and a high speed amplifier.

4. The receiver of claim 1 wherein the substrate comprises silicon and the plurality of imaging cells comprises a) an array of photodetectors comprising germanium and b) silicon readout circuits to provide an electrical representation of the variation of light with position across the surface of the receiver.

5. The receiver of claim 1 wherein the plurality of imaging cells are disposed about the receiver cell in a co-planar imaging array.

6. The receiver of claim 1 wherein the receiver cell and the imaging cells receive light from the signal beam in a single optical path.

7. The receiver of claim 1 further comprising a positioning mechanism and a tracking control circuit, the tracking control circuit responsive to electrical output from the imaging cells to generate a tracking signal for directing the positioning mechanism to maintain accurate pointing of the receiver toward the source of the signal beam.

8. The receiver of claim 1 wherein each imaging cell comprises a photodetector and an integrating circuit to accumulate electrical energy from illumination over a period of time.

9. A line of sight optical communication system comprising:

an optical transmitter for transmitting a beam of modulated light through atmosphere or space, and

an optical receiver system for receiving the transmitted beam, the receiver comprising collection optics for collecting and concentrating the beam, a variable focal length lens for collimating or converging the concentrated beam, and an optical receiver according to claim 1.

10. The communication system of claim 9 wherein the collimated beam is distributed over substantially all of the imaging cells and the converged beam is concentrated essentially on the receiver cell.

11. The communication system of claim 9 wherein the power in imaging cells adjacent the receiver cell is monitored to detect deviation of the optical beam from the receiver cell.

12. An optical imaging array comprising:

a substrate comprising a first photosensitive crystalline semiconductor material; and

integrated on the substrate a plurality of photodetectors comprising photosensitive crystalline semiconductor material wherein the photosensitive material of at least one of the photodetectors is the first photosensitive material and the photosensitive material of at least another of the photodetectors is a second photosensitive semiconductor chemically different from the first material.

13. The imaging array of claim 12 wherein the first photosensitive material is silicon and the second photosensitive material is selected from the group consisting of germanium, germanium alloy, InGaAs and HgCdTe.

14. The imaging array of claim 12 wherein the second photosensitive material is epitaxially grown on the first photosensitive material.

15. The imaging array of claim 12 wherein the first photosensitive material is crystalline silicon and the second photosensitive material is a photosensitive crystalline semiconductor epitaxially grown on the silicon.

16. The imaging array of claim 15 wherein the second photosensitive material comprises germanium.

17. An optical imaging device comprising:

a substrate; and

integrated on the substrate a plurality of photodetectors wherein at least one of the photodetectors is a high speed photodetector with a response speed of at least 10 megahertz and at least one of the photodetectors is a low speed photodetector with a response speed of less than 500 kilohertz.

18. The device of claim 17 wherein the high speed photodetector has a speed of one gigahertz or more and the low speed photodetector has a speed of 30 hertz or less.

19. The device of claim 17 wherein the plurality of photodetectors are disposed in a substantially planar array.

20. The device of claim 19 wherein there are a plurality of low speed photodetectors and the low speed photodetectors are disposed peripherally around at least one high speed photodetector.

21. The device of claim 17 wherein the photodetectors are coplanar to within 10 micrometers or less.