Vertical output couplers for photonic devices

• US 9,829,631 B2
• Filed: 04/20/2016
• Issued: 11/28/2017
• Est. Priority Date: 04/20/2015
• Status: Active Grant

• Current Assignee: Skorpios Technologies Inc.
• Original Assignee: Skorpios Technologies Inc.
• Inventors: Lambert, Damien
• Primary Examiner(s): Tran, Thanh Y
• Assistant Examiner(s): CRITE, ANTONIO B
• Application Number:
  US15/133,898
• Publication Number:
  US 20160306110A1
• Time in Patent Office: 587 Days
• Field of Search: 385 14, 385 88, 385132, 257186, 438 48, 216 24
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12097 Ridge, rib or the like
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 2006/12169 Annealing
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/132 by deposition of thin films
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence

Abstract

A method forms a vertical output coupler for a waveguide that propagates light along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer. The method includes etching the waveguide to remove a portion of the waveguide. The etching forms at least a first plane that is at an edge of the waveguide, is adjacent to the removed portion of the waveguide, and is tilted at a vertical angle between 20 degrees and 70 degrees with respect to the propagation direction. The method further includes coating the first tilted plane with a reflective metal to form a mirror, such that the mirror reflects the light into a direction having a vertical component.

Claims

1. A method of forming a vertical output coupler for a waveguide that propagates light, along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer, the method comprising:

etching the waveguide material to form the waveguide;

etching the waveguide material to remove at least a first portion of the waveguide, wherein the etching forms;

at least a first tilted plane in the waveguide material, and

a space between an unetched portion of the waveguide and the first tilted plane;

coating the first tilted plane with a reflective metal to form a tilted mirror; and

depositing an index matching material into the space between the unetched portion of the waveguide and the tilted mirror so that light propagating through the waveguide into the space continues through the index matching material to the tilted mirror, and the tilted mirror reflects the light upwardly, wherein depositing the index matching material into the space between the unetched portion of the waveguide and the tilted mirror comprises depositing amorphous silicon.

2. The method of claim 1, further comprising annealing the amorphous silicon, to convert the amorphous silicon to polysilicon.

11. The method of claim 1, further comprising laterally patterning the index matching material to form a waveguide ridge that adjoins a waveguide ridge of the unetched portion of the waveguide.

12. The method of claim 11, wherein laterally patterning the index matching material to form the waveguide ridge comprises patterning the index matching material with a profile that tapers outwardly from an initial width matching the waveguide ridge of the unetched portion of the waveguide, to a final width proximate the tilted mirror so that a beam size of the light propagating through the waveguide expands as it propagates toward the tilted mirror.

3. A method of forming a vertical output coupler for a waveguide that propagates light, along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer, the method comprising:

etching the waveguide material to form the waveguide;

etching the waveguide material to remove at least a first portion of the waveguide, wherein the etching forms;

at least a first tilted plane in the waveguide material, and

a space between an unetched portion of the waveguide and the first tilted plane;

coating the first tilted plane with a reflective metal to form a tilted mirror; and

depositing an index matching material into the space between the unetched portion of the waveguide and the tilted mirror so that light propagating through the waveguide into the space continues through the index matching material to the tilted mirror, and the tilted mirror reflects the light upwardly, wherein depositing the index matching material into the space between the unetched portion of the waveguide and the tilted mirror comprises depositing the index matching material to a thickness that substantially exceeds a height of the unetched portion of the waveguide;

the method further comprising etching the index matching material to form a bridge between the unetched portion of the waveguide and the tilted mirror, the bridge being approximately equal in height to the unetched portion of the waveguide.

4. The method of claim 3, further comprising planarizing the index matching material, prior to etching the index matching material to form the bridge between the unetched portion of the waveguide and the tilted mirror.

5. The method of claim 3, further comprising laterally patterning the index matching material to form a waveguide ridge that adjoins a waveguide ridge of the unetched portion of the waveguide.

6. The method of claim 5, wherein laterally patterning the index matching material to form the waveguide ridge comprises patterning the index matching material with a profile that tapers outwardly from an initial width matching the waveguide ridge of the unetched portion of the waveguide, to a final width proximate the tilted mirror so that a beam size of the light propagating through the waveguide expands as it propagates toward the tilted mirror.

13. The method of claim 3, wherein the index matching material is one of amorphous silicon and polysilicon.

14. The method of claim 3, wherein the index matching material is amorphous silicon, and further comprising annealing the amorphous silicon, to convert the amorphous silicon to polysilicon.

7. A method of forming a vertical output coupler for a waveguide that propagates light, along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer, the method comprising:

etching the waveguide material to form the waveguide;

etching the waveguide material to remove at least a first portion of the waveguide, wherein the etching forms;

at least a first tilted plane in the waveguide material,

a space between an unetched portion of the waveguide and the first tilted plane, and

a second tilted plane that bounds the unetched portion of the waveguide;

coating the first tilted plane with a reflective metal to form a tilted mirror;

depositing an index matching material into the space between the unetched portion of the waveguide and the tilted mirror so that light propagating through the waveguide into the space continues through the index matching material to the tilted mirror, and the tilted mirror reflects the light upwardly;

forming a photoresist mask over the first tilted plane;

etching away the second tilted plane to enlarge the space, leaving a substantially vertical end face on the unetched portion of the waveguide, while the photoresist mask protects the first tilted plane; and

etching a portion of the buried oxide layer beneath the enlarged space, after etching away the second tilted plane and before depositing the index matching material;

wherein the steps of forming the photoresist mask and etching away the second tilted plane precede coating the first tilted plane with the reflective metal.

15. The method of claim 7, wherein the index matching material is one of amorphous silicon and polysilicon.

16. The method of claim 7, wherein the index matching material is amorphous silicon, and further comprising annealing the amorphous silicon, to convert the amorphous silicon to polysilicon.

8. A method of forming a vertical output coupler for a waveguide that propagates light, along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer, the method comprising:

etching the waveguide material to form the waveguide;

etching the waveguide material to remove at least a first portion of the waveguide, wherein the etching forms;

at least a first tilted plane in the waveguide material,

a space between an unetched portion of the waveguide and the first tilted plane, and

a second tilted plane that bounds the unetched portion of the waveguide;

coating the first tilted plane with a reflective metal to form a tilted mirror;

depositing an index matching material into the space between the unetched portion of the waveguide and the tilted mirror so that light propagating through the waveguide into the space continues through the index matching material to the tilted mirror, and the tilted mirror reflects the light upwardly;

forming a photoresist mask over the first tilted plane;

etching away the second tilted plane to enlarge the space, leaving a substantially vertical end face on the unetched portion of the waveguide, while the photoresist mask protects the first tilted plane; and

further comprising, after coating the first tilted plane with the reflective metal to form the tilted mirror;

depositing a support material over the enlarged space and unetched portions of the waveguide; and

etching back the support material deposited over the space until a top surface of the etched back support material substantially coincides with a top surface of the buried oxide layer, so that the remaining support material deposited over the space forms a bridge support for the index matching material;

wherein;

the steps of depositing the support material, planarizing the support material and etching the support material precede the step of depositing the index matching material; and

the steps of forming the photoresist mask and etching away the second tilted plane precede coating the first tilted plane with the reflective metal.

9. The method of claim 8, further comprising planarizing the support material deposited over the space and the unetched portions of the waveguide prior to the step of etching back the support material.

17. The method of claim 8, wherein the index matching material is one of amorphous silicon and polysilicon.

18. The method of claim 8, wherein the index matching material is amorphous silicon, and further comprising annealing the amorphous silicon, to convert the amorphous silicon to polysilicon.

10. A method of forming a vertical output coupler for a waveguide that propagates light, along a horizontal propagation direction, through a waveguide material that overlies a buried oxide layer, the method comprising:

etching the waveguide material to form the waveguide;

etching the waveguide material to remove at least a first portion of the waveguide, wherein the etching forms;

at least a first tilted plane in the waveguide material, and

a space between an unetched portion of the waveguide and the first tilted plane;

coating the first tilted plane with a reflective metal to form a tilted mirror;

depositing an index matching material into the space between the unetched portion of the waveguide and the tilted mirror so that light propagating through the waveguide into the space continues through the index matching material to the tilted mirror, and the tilted mirror reflects the light upwardly; and

depositing an antireflective coating over the tilted mirror and the index matching material.

19. The method of claim 10, wherein the index matching material is one of amorphous silicon and polysilicon.

20. The method of claim 10, wherein the index matching material is amorphous silicon, and further comprising annealing the amorphous silicon, to convert the amorphous silicon to polysilicon.