Integrated photonics mode expander

Patent metadata

Field	Value
Publication number	US-10895686-B2
Application number	US-201815968454-A
Country	US
Kind code	B2
Filing date	May 1, 2018
Priority date	Aug 30, 2011
Publication date	Jan 19, 2021
Grant date	Jan 19, 2021

Abstract

A method of fabricating a waveguide mode expander includes providing a substrate including a waveguide, bonding a chiplet including multiple optical material layers in a mounting region adjacent an output end of the waveguide, and selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end to a distal end of the chiplet. The first optical material layer supports an input mode substantially the same size as a mode exiting the waveguide. One or more of the overlying layers, when combined with the first layer, support a larger, output optical mode size. Each tapered stage of the mode expander is formed of a portion of a respective layer of the chiplet. The first layer and the tapered stages form a waveguide mode expander that expands an optical mode of light traversing the chiplet.

First claim

What is claimed is:

1. A method of fabricating a waveguide mode expander, the method comprising:
providing a silicon on insulator (SOI) substrate comprising a waveguide, wherein:
the waveguide defines a waveguide thickness and terminates at an output end, and
the waveguide supports an optical mode of an initial mode size at the output end;

forming a mounting region adjacent the output end of the waveguide;
providing a multi-layer chiplet comprising an optical material and one or more additional materials that are different from the optical material, wherein
a first layer of the optical material defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size,
one or more overlying layers of the optical material define thicknesses that, when combined with the first layer, support an output optical mode size that is larger than the initial mode size, and
layers of the one or more additional materials are interspersed between the first layer and each of the one or more overlying layers of the optical material;

bonding the chiplet in the mounting region; and
selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the waveguide, to a distal end of the chiplet, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial optical mode size entering the proximal end, to the output optical mode size at the distal end.

2. The method of claim 1 wherein the waveguide comprises at least one of crystalline silicon, polycrystalline silicon and amorphous silicon.

3. A method of fabricating a waveguide mode expander, the method comprising:
providing a silicon on insulator (SOI) substrate comprising a waveguide, wherein:
the waveguide defines a waveguide thickness and terminates at an output end, and
the waveguide supports an optical mode of an initial mode size at the output end;

forming a mounting region adjacent the output end of the waveguide;
providing a multi-layer chiplet comprising one or more optical materials, wherein:
a lower layer of the chiplet comprises a metal layer,
a first layer of the one or more optical materials defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size, and
one or more overlying layers define thicknesses that, when combined with the first layer, support an output optical mode size that is larger than the initial mode size;

bonding the chiplet in the mounting region, wherein bonding the chiplet comprises forming a metal to semiconductor bond with the SOI substrate; and
selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the waveguide, to a distal end of the chiplet, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial optical mode size entering the proximal end, to the output optical mode size at the distal end.

4. The method of claim 1 wherein the first layer thickness is equal to the waveguide thickness.

5. A method of fabricating a waveguide mode expander, the method comprising:
providing a silicon on insulator (SOI) substrate comprising a waveguide, wherein:
the waveguide defines a waveguide thickness and terminates at an output end, and
the waveguide supports an optical mode of an initial mode size at the output end;

forming a mounting region adjacent the output end of the waveguide;
providing a multi-layer chiplet comprising one or more optical materials, wherein
a first layer of the one or more optical materials defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size, and
one or more overlying layers define thicknesses that, when combined with the first layer, support an output optical mode size that is larger than the initial mode size, and wherein providing the multi-layer chiplet comprises:
successively depositing the first layer and the one or more overlying layers on a substrate; and
singulating the substrate to form multiple ones of the chiplet;

bonding the chiplet in the mounting region; and
selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the waveguide, to a distal end of the chiplet, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial optical mode size entering the proximal end, to the output optical mode size at the distal end.

6. The method of claim 5 wherein the substrate comprises a compound semiconductor.

7. The method of claim 6 wherein the compound semiconductor is characterized by a substrate lattice constant, and wherein the first layer and the one or more overlying layers are characterized by lattice constants that match the substrate lattice constant.

8. The method of claim 5 wherein providing the multi-layer chiplet comprises:
forming the first layer and alternating ones of the one or more overlying layers of a first one of the one or more optical materials; and
forming etch stop layers, that are interspersed between the first layer and the alternating ones of the one or more overlying layers, of a different material than the first one of the one or more optical materials.

9. The method of claim 8 wherein selectively removing portions of the chiplet comprises:
applying a photoresist mask to protect a tapered portion of the chiplet; and
etching a layer of the chiplet that is not protected by photoresist until an underlying etch stop layer is exposed.

10. The method of claim 9 wherein applying a photoresist mask and etching a layer of the chiplet are repeated for each of the one or more overlying layers and for the first layer.

11. The method of claim 9 , further comprising removing the underlying etch stop layer.

12. The method of claim 11 , wherein an etch that etches the layer of the chiplet that is not protected by photoresist is selective to the underlying etch stop layer, and an etch that removes the underlying etch stop layer is selective to a layer of the chiplet that underlies the underlying etch stop layer.

13. The method of claim 1 ,
wherein bonding the chiplet in the mounting region includes positioning the chiplet such that a gap exists between the output end of the waveguide and the chiplet;
and further comprising forming an optical bridge between the waveguide mode expander and the waveguide, such that the optical bridge spans the gap.

14. A method of coupling a first waveguide with a second waveguide, the method comprising:
providing a silicon on insulator (SOI) substrate comprising the first waveguide and the second waveguide, wherein:
the first waveguide defines a first waveguide thickness and terminates at an output end,
the first waveguide supports a first optical mode of an initial mode size at the output end,
the second waveguide defines a second

Assignees

• Skorpios Tech Inc

Inventors

• Lambert Damien
• Li Guoliang
• Zyskind John
• Krasulick Stephen B

Classifications

• G02B6/1228 Primary

  Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305) · CPC title

• G02B2006/12061

  Silicon · CPC title

• G02B6/132

  by deposition of thin films · CPC title

• G02B6/136

  by etching · CPC title

• G02B2006/12152

  Mode converter · CPC title