Angled grating couplers with inclined side edge portions

Patent metadata

Field	Value
Publication number	US-11567266-B1
Application number	US-202117551377-A
Country	US
Kind code	B1
Filing date	Dec 15, 2021
Priority date	Dec 15, 2021
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

Structures for a grating coupler and methods of fabricating a structure for a grating coupler. The structure includes a grating coupler having a central portion and edge portions. The central portion and the edge portions define a sidewall, and the central portion and the edge portions have a first longitudinal axis along which the edge portions are arranged in a spaced relationship. Each edge portion projects from the sidewall at an angle relative to the first longitudinal axis. A waveguide core is optically coupled to the grating coupler. The first longitudinal axis is aligned in a first direction, and the waveguide core has a second longitudinal axis that is aligned in a second direction different from the first direction.

First claim

What is claimed is:

1. A structure comprising:
a grating coupler including a first plurality of semiconductor layers, a second plurality of semiconductor layers, a central portion, and a first plurality of edge portions, the central portion and the first plurality of edge portions defining a first sidewall, the central portion and the first plurality of edge portions having a first longitudinal axis along which the first plurality of edge portions are arranged in a first spaced relationship, the first longitudinal axis aligned in a first direction, each of the first plurality of edge portions projecting from the first sidewall at a first angle relative to the first longitudinal axis, the first plurality of semiconductor layers and the second plurality of semiconductor layers alternating in a layer stack along the first longitudinal axis, and the second plurality of semiconductor layers recessed at the first sidewall relative to the first plurality of semiconductor layers such that the first plurality of semiconductor layers define the first plurality of edge portions; and
a waveguide core optically coupled to the grating coupler, the waveguide core having a second longitudinal axis, and the second longitudinal axis aligned in a second direction different from the first direction.

2. The structure of claim 1 wherein the grating coupler includes a second plurality of edge portions, the central portion and the second plurality of edge portions define a second sidewall opposite the first sidewall, the second plurality of edge portions are arranged in a second spaced relationship along the first longitudinal axis, and each of the second plurality of edge portions projects from the second sidewall at a second angle relative to the first longitudinal axis.

3. The structure of claim 2 wherein the first angle is equal to the second angle.

4. The structure of claim 1 wherein the grating coupler includes a second plurality of edge portions that are connected by the central portion, the central portion and the second plurality of edge portions define a second sidewall opposite to the first sidewall, the second plurality of edge portions are arranged in a second spaced relationship along the first longitudinal axis, and each of the second plurality of edge portions projects from the second sidewall transverse to the first longitudinal axis.

5. The structure of claim 1 wherein the first angle varies with position along the first longitudinal axis.

6. The structure of claim 1 wherein the first plurality of edge portions have a spacing in the first direction that varies with position along the first longitudinal axis.

7. The structure of claim 1 wherein the first plurality of edge portions have equal first angles.

8. The structure of claim 1 wherein the first plurality of semiconductor layers comprise silicon, and the second plurality of semiconductor layers comprise silicon-germanium.

9. The structure of claim 1 wherein the first plurality of semiconductor layers comprise silicon with a first concentration of a dopant, and the second plurality of semiconductor layers comprise silicon with a second concentration of the dopant that is greater than the first concentration of the dopant.

10. The structure of claim 1 further comprising:
an optical component adjacent to the central portion of the grating coupler, the optical component aligned with the first longitudinal axis.

11. The structure of claim 1 wherein the first direction is a vertical direction, and the second direction is a horizontal direction.

12. The structure of claim 1 wherein the first direction is oriented transverse to the second direction.

13. A structure comprising:
a grating coupler including a central portion and a first plurality of edge portions, the central portion and the first plurality of edge portions defining a first sidewall, the central portion and the first plurality of edge portions having a first longitudinal axis along which the first plurality of edge portions are arranged in a first spaced relationship, the first longitudinal axis aligned in a first direction, and each of the first plurality of edge portions projecting from the first sidewall at a first angle relative to the first longitudinal axis;
a waveguide core optically coupled to the grating coupler, the waveguide core having a second longitudinal axis, and the second longitudinal axis aligned in a second direction different from the first direction; and
a faceted semiconductor layer positioned in the first direction between the waveguide core and the central portion of the grating coupler.

14. The structure of claim 13 wherein the faceted semiconductor layer includes a surface that is inclined at the first angle, and the grating coupler is positioned on the surface of the faceted semiconductor layer.

15. The structure of claim 13 wherein the first plurality of edge portions have equal first angles.

16. The structure of claim 13 wherein the first direction is a vertical direction, and the second direction is a horizontal direction.

17. A method comprising:
forming a grating coupler including a central portion and a first plurality of edge portions, wherein the central portion and the first plurality of edge portions define a first sidewall, the central portion and the first plurality of edge portions have a first longitudinal axis along which the first plurality of edge portions are arranged in a first spaced relationship, and each of the first plurality of edge portions projects from the first sidewall at a first angle relative to the first longitudinal axis; and
forming a waveguide core optically coupled to the grating coupler, wherein the waveguide core has a second longitudinal axis, the first longitudinal axis is aligned in a first direction and the second longitudinal axis is aligned in a second direction different from the first direction, and
wherein forming the grating coupler including the central portion and the first plurality of edge portions comprises:
epitaxially growing a layer stack including a first plurality of semiconductor layers and a second plurality of semiconductor layers that alternate with the first plurality of semiconductor layers in the first direction along the first longitudinal axis; and
recessing the second plurality of semiconductor layers relative to the first plurality of semiconductor layers at the first sidewall such that the first plurality of semiconductor layers define the first plurality of edge portions.

18. The method of claim 17 wherein the grating coupler includes a second plurality of edge portions, the central portion and the second plurality of edge portions define a second sidewall opposite the first sidewall, the second plurality of edge portions are arranged in a second spaced relationship along the first longitudinal axis, and each of the second plurality of edge portions projects from the second sidewall at a second angle relative to the first longitudinal axis.

19. The method of claim 17 wherein the first angle varies with position along the first longitudinal axis.

20. The method of claim 17 wherein the first plurality of edge portions have a spacing in the first direction that varies with position along the first longitudinal axis.

Assignees

• Globalfoundries Us Inc

Inventors

• Holt Judson
• Bian Yusheng
• Liu Qizhi
• Strehlow Elizabeth

Classifications

• G02B6/29323

  Coupling to or out of the diffractive element through the lateral surface of the light guide (evanescent grating couplers G02B6/29332) · CPC title

• G02B2006/12107

  Grating · CPC title

• G02B6/4295

  coupling with semiconductor devices activated by light through the light guide, e.g. thyristors, phototransistors · CPC title

• G02B6/124 Primary

  Geodesic lenses or integrated gratings · CPC title

• G02B6/34 Primary

  utilising prism or grating {(G02B6/293 takes precedence)} · CPC title