Waveguide coupler having continuous three-dimensional tapering

• US 8,472,766 B2
• Filed: 08/12/2010
• Issued: 06/25/2013
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Spector, Steven Jay, Swint, Reuel Bennett, Popovic, Milos
• Primary Examiner(s): KIM, ELLEN E
• Application Number:
  US12/855,032
• Publication Number:
  US 20110170825A1
• Time in Patent Office: 1,048 Days
• Field of Search: 385/43, 385129-131, 385/28, 385/39, 438/31, 257/E33.067
• US Class Current: 385/43
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/136 by etching

Abstract

A solid state waveguide coupler is provided including a first coupler end disposed on a solid state material substrate for connection to a first solid state waveguide located on the substrate and a second coupler end disposed on the substrate for connection to a second waveguide located on the substrate. A coupling span, comprising a waveguide material layer on the substrate, is disposed between the first and second coupler ends and tapers between a height of the first waveguide and a height of the second waveguide, tapers between a width of the first waveguide and a width of the second waveguide, and includes curved sidewalls along at least a portion of the tapered coupling span. In a method for fabricating the waveguide coupler, material is isotropically removed from a waveguide material layer on the substrate to produce tapered surfaces between the first waveguide and the second waveguide.

Claims

1. A solid state waveguide coupler comprising:

a first coupler end disposed on a solid state material substrate for connection to a first solid state waveguide located on the substrate;

a second coupler end disposed on the solid state material substrate for connection to a second solid state waveguide located on the substrate; and

a coupling span, comprising a waveguide material layer on the solid state substrate, disposed between the first and second coupler ends and tapering between a height of the first waveguide and a height of the second waveguide, tapering between a width of the first waveguide and a width of the second waveguide, and including curved sidewalls along at least a portion of the tapered coupling span.

2. The solid state waveguide coupler of claim 1 wherein the first waveguide, the second waveguide, and the coupling span each comprise the waveguide material layer on the solid state substrate.

3. The solid state waveguide coupler of claim 1 wherein the waveguide material layer comprises a semiconducting material.

4. The solid state waveguide coupler of claim 1 wherein the waveguide material layer is selected from the group consisting of crystalline silicon, polycrystalline silicon, amorphous silicon, and silicon nitride.

5. The solid state waveguide coupler of claim 1 wherein the first waveguide comprises a rib waveguide and the second waveguide comprises a strip waveguide.

6. The solid state waveguide coupler of claim 1 wherein the first and second waveguides each comprise rib waveguides.

7. The solid state waveguide coupler of claim 1 wherein the first and second waveguides each comprise strip waveguides.

8. The solid state waveguide coupler of claim 1 wherein the coupling span taper between a height of the first waveguide and a height of the second waveguide comprises a tapered sidewall including no vertical wall along the coupling span.

9. The solid state waveguide coupler of claim 1 wherein the coupling span taper between a width of the first waveguide and a width of the second waveguide comprises a tapered wall including no horizontal wall along the coupling span.

10. The solid state waveguide coupler of claim 1 wherein the coupling span is characterized by a width and by a height each as a function of span position that prohibits crossing of TE and TM optical modes along the coupling span.

11. The solid state waveguide coupler of claim 1 wherein the coupling span is at least about 100 μ

m in length.

12. The solid state waveguide coupler of claim 1 wherein at least one of the first and the second coupler ends comprises a tapered point.

13. The solid state waveguide coupler of claim 1 wherein portions of sidewalls of the coupling span are characterized by a profile that is isotropic with respect to vertical and horizontal directions.

14. The solid state waveguide coupler of claim 1 wherein the coupling span is tapered in all three dimensions.

15. The solid state waveguide coupler of claim 1 wherein the substrate comprises a silicon-on-insulator substrate.

16. The solid state waveguide coupler of claim 1 further comprising an undercladding layer on the solid state substrate under the waveguide material layer on the solid state substrate.