Waveguide mode expander having non-crystalline silicon features

Patent metadata

Field	Value
Publication number	US-2021116640-A1
Application number	US-202016985860-A
Country	US
Kind code	A1
Filing date	Aug 5, 2020
Priority date	May 27, 2014
Publication date	Apr 22, 2021
Grant date	—

Abstract

A waveguide mode expander couples a smaller optical mode in a semiconductor waveguide to a larger optical mode in an optical fiber. The waveguide mode expander comprises a shoulder and a ridge. In some embodiments, the ridge of the waveguide mode expander has a plurality of stages, the plurality of stages having different widths at a given cross section.

First claim

1 . (canceled)

2 . A multistage coupler that shifts a height of an optical beam relative to a substrate, comprising:
the substrate, wherein the substrate defines an upper surface; a lower cladding layer; a first stage and a final stage, wherein:
the first stage is formed of amorphous silicon or polysilicon, and has a higher index of refraction than the lower cladding layer;
the first stage forms an input end that is configured to receive the optical beam from an input waveguide that propagates the optical beam along a propagation direction;
the lower cladding layer is disposed between the first stage and the upper surface;
the first stage is disposed at a first height, relative to the upper surface, from the input end to a first-stage end;
the first stage forms a first-stage cross section, transverse to the propagation direction, that tapers along the propagation direction, wherein the first-stage end is narrower than the input end;
the first stage is optically coupled with the final stage, and is in direct physical contact with the final stage, with no intervening material therebetween;
the final stage forms an output end that is configured to transmit the optical beam into an output waveguide at a second height relative to the upper surface;
the final stage is formed of amorphous silicon or polysilicon, and has a higher index of refraction than the lower cladding layer;
the final stage is disposed at the second height relative to the upper surface from a final-stage end to the output end, the second height being greater than the first height;
the optical beam propagates directly from the first stage into the final stage; and
the final stage forms a final-stage cross section, transverse to the propagation direction, that widens along the propagation direction, wherein the output end is wider than the final-stage end.

3 . The multistage coupler of claim 2 , wherein the first-stage cross section at the input end of the first stage supports an optical mode of an initial mode size, and the final-stage cross section at the output end of the final stage supports an optical mode of a final mode size that is the same as the initial mode size.

4 . The multistage coupler of claim 2 , wherein the first-stage cross section at the input end of the first stage supports an optical mode of an initial mode size, and the final-stage cross section at the output end of the final stage supports an optical mode of a final mode size that is different from the initial mode size.

5 . The multistage coupler of claim 2 , further comprising an upper cladding layer, wherein:
the first stage and the final stage are disposed between the upper cladding layer and the upper surface, the upper cladding layer has a lower index of refraction than both the first stage and the final stage.

6 . The multistage coupler of claim 2 , further comprising the input waveguide, wherein:
the input waveguide is formed of crystalline silicon, and is disposed above the lower cladding layer; and the input waveguide is configured to transmit the optical beam into the input end of the first stage.

7 . The multistage coupler of claim 2 , further comprising the output waveguide, wherein:
the output waveguide is formed of crystalline silicon, a III-V compound or a II-VI compound; and the output waveguide is configured to receive the optical beam from the output end of the final stage.

8 . A multistage coupler that shifts a height of an optical beam relative to a substrate, comprising:
the substrate, wherein the substrate defines an upper surface; a lower cladding layer; a first stage, an intermediate stage, and a final stage, wherein:
the first stage is formed of amorphous silicon or polysilicon, and has a higher index of refraction than the lower cladding layer;
the first stage forms an input end that is configured to receive the optical beam from an input waveguide that propagates the optical beam along a propagation direction;
the lower cladding layer is disposed between the first stage and the upper surface;
the first stage is disposed at a first height, relative to the upper surface, from the input end to a first-stage end;
the first stage forms a first-stage cross section, transverse to the propagation direction, that tapers along the propagation direction, wherein the first-stage end is narrower than the input end;
the first stage is optically coupled with the final stage;
the intermediate stage is formed of amorphous silicon or polysilicon, and is in direct physical contact with the first stage, with no intervening material therebetween;
the intermediate stage is disposed at a second height relative to the upper surface;
the second height is greater than the first height;
the final stage forms an output end that is configured to transmit the optical beam into an output waveguide at a third height relative to the upper surface;
the final stage is formed of amorphous silicon or polysilicon, and has a higher index of refraction than the lower cladding layer;
the final stage is disposed at the third height relative to the upper surface from a final-stage end to the output end, the third height being greater than the second height;
the optical beam propagates directly from the first stage into the final stage; and
the final stage forms a final-stage cross section, transverse to the propagation direction, that widens along the propagation direction, wherein the output end is wider than the final-stage end.

9 . The multistage coupler of claim 8 , wherein:
the intermediate stage defines an intermediate-stage cross section, transverse to the propagation direction, and the intermediate-stage cross section widens or narrows along the propagation direction.

10 . The multistage coupler of claim 9 , wherein:
the intermediate stage defines an intermediate stage beginning, an intermediate stage middle portion and an intermediate-stage end, the intermediate stage beginning couples optically with the first stage; the intermediate-stage cross section forms a first taper that widens along the propagation direction from the intermediate stage beginning to the intermediate stage middle portion; the intermediate-stage end couples optically with the final stage; and the intermediate-stage cross section forms a second taper that narrows along the propagation direction from the intermediate stage middle portion to the intermediate-stage end.

11 . The multistage coupler of claim 8 , wherein the final stage is in direct contact with the intermediate stage, with no intervening material therebetween, and the optical beam propagates directly from the intermediate stage into the final stage.

12 . The multistage coupler of claim 8 , wherein the intermediate stage comprises a first intermediate stage and a second intermediate stage, each of the first and second intermediate stages being formed of amorphous silicon or polysilicon.

13 . A method of shifting a height of an optical beam relative to a substrate, comprising:
receiving the optical beam at an input end of a multistage coupler that is coupled with the substrate, wherein the input end of the multistage coupler defines a first height relative to an upper surface of the substrate; propagating the optical beam through the multistage coupler, wherein the multistage coupler comprises a first stage and a final stage, and wherein:
the first stage is disposed at the first height, relative to the upper surface, from the input end to a first-stage end, and
the first stage is formed of amorphous silicon or polysilicon, and tapers along a propagation direction that extends from the input end to the first-stage end,

Assignees

• Skorpios Tech Inc

Inventors

• Li Guoliang
• Lambert Damien
• Kumar Nikhil

Classifications

• G02B6/136

  by etching · CPC title

• G02B2006/12061

  Silicon · CPC title

• G02B6/305

  and having an integrated mode-size expanding section, e.g. tapered waveguide · CPC title

• G02B2006/12038

  Glass (SiO2 based materials) · CPC title

• G02B2006/12097

  Ridge, rib or the like · CPC title