Integrated photonic-mirror test circuit

Patent metadata

Field	Value
Publication number	US-10113934-B2
Application number	US-201715804956-A
Country	US
Kind code	B2
Filing date	Nov 6, 2017
Priority date	Nov 20, 2015
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

A reflectivity test circuit is described. The reflectivity test circuit includes a symmetric structure that cancels errors in the reflectivity measurements. In particular, the reflectivity test circuit includes an optical waveguide that is optically coupled to two optical ports and two optical couplers. The optical couplers are optically coupled to adjacent optical waveguides, at least one of which is optically coupled to a third optical port and the mirror. Moreover, a length of the optical waveguide is chosen to match the round-trip optical path length in at least the one of the adjacent optical waveguides. During operation, control logic determines the reflectivity of the mirror based at least on a ratio of an optical power measured on one of the two optical ports to an input optical power on the third optical port.

First claim

What is claimed is:

1. An integrated circuit, comprising a reflectivity test circuit, wherein the reflectivity test circuit includes:
a first mirror;
a first photodetector that, during operation, measures a first optical power;
a first optical waveguide having a first end optically coupled to the first mirror and a second end optically coupled to the first photodetector;
a first optical coupler;
a first optical port that, during operation, selectively receives first input optical power;
a second optical port that, during operation, selectively receives second input optical power;
a second optical waveguide optically coupled to the first optical waveguide by the first optical coupler, wherein a first end of the second optical waveguide is optically coupled to the first optical port and a second end of the second optical waveguide is optically coupled to the second optical port;
a second optical coupler;
a second mirror;
a second photodetector that, during operation, measures a second optical power;
a third optical waveguide optically coupled to the second optical waveguide by the second optical coupler, wherein a first end of the third optical waveguide is optically coupled to the second mirror and a second end of the third optical waveguide is optically coupled to the second photodetector; and
control logic electrically coupled to the first photodetector and the second photodetector, wherein, during operation, the control logic determines a reflectivity of the first mirror based on a first ratio of the first optical power and the second optical power when the first input optical power is received on the first optical port.

2. The integrated circuit of claim 1 , wherein the first optical port and the second optical port include vertical grating couplers.

3. The integrated circuit of claim 1 , wherein the integrated circuit comprises:
a substrate;
a buried-oxide layer disposed on the substrate; and
a semiconductor layer disposed on the buried-oxide layer;
wherein the first optical waveguide, the first optical coupler, the second optical waveguide, the second optical coupler and the third optical waveguide are, at least in part, included in the semiconductor layer.

4. The integrated circuit of claim 1 , wherein the first optical waveguide has a first length equal to L, the second optical waveguide has a second length equal to 2·L, and the third optical waveguide has a third length equal to L.

5. The integrated circuit of claim 1 , wherein, during operation, the control logic determines the reflectivity at different wavelengths.

6. The integrated circuit of claim 1 , wherein the first mirror and the second mirror include distributed Bragg reflectors.

7. The integrated circuit of claim 1 , wherein during operation, the control logic determines the reflectivity of the first mirror based on a product of the first ratio and a second ratio of the second optical power and the first optical power when the second input optical power is received on the second optical port.

8. A method for determining a reflectivity of a first mirror, the method comprising:
receiving first input optical power at a first optical port;
conveying a first portion of the first input optical power to the first mirror using a first optical waveguide;
optically coupling a second portion of the first input optical power to a second optical waveguide using a first optical coupler;
conveying a third portion of the first input optical power to a first photodetector using the second optical waveguide;
measuring a first optical power using the first photodetector;
conveying a fourth portion of the first input optical power to a second photodetector using the second optical waveguide;
measuring a second optical power using the second photodetector; and
determining the reflectivity of the first mirror based on a first ratio of the first optical power and the second optical power, wherein the first optical waveguide has a first length equal to L, the second optical waveguide has a second length equal to 2·L, and the third optical waveguide has a third length equal to L.

Assignees

• Oracle Int Corp

Inventors

• Bovington Jock T
• Zheng Xuezhe

Classifications

• G02B6/125

  Bends, branchings or intersections · CPC title

• G02B6/2938

  for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM · CPC title

• G02B6/26

  Optical coupling means (G02B6/36, G02B6/42 take precedence) · CPC title

• G01M11/005 Primary

  Testing of reflective surfaces, e.g. mirrors · CPC title

• G02B2006/12104

  Mirror; Reflectors or the like · CPC title