Method of making an enhanced coupling strength grating having a cover layer

Patent metadata

Field	Value
Publication number	US-10620378-B2
Application number	US-201916522544-A
Country	US
Kind code	B2
Filing date	Jul 25, 2019
Priority date	Sep 5, 2013
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

The present invention includes an optical waveguide with a grating and a method of making the same for increasing the effectiveness of the grating. In one example, the grating is at least partially covered by a liner layer disposed on at least a portion of a grating; and a cover layer disposed on the liner layer, wherein a first material selected for the core and ridges and a second material selected for the liner layer are selected to provide a difference in the index of refraction between the first and second material that is sufficient to provide a contrast therebetween.

First claim

What is claimed is:

1. A method of making a grating comprising:
depositing on a first portion of substrate, a core on the substrate, a superstrate on the core, and a photoresist on the superstrate;
etching the superstrate to the core;
etching through a grating mask formed on the core to form the grating comprising one or more ridges and one or more grooves, wherein the one or more grooves are adjacent to, or between the one or more ridges;
removing the grating mask;
depositing a liner layer on the grating, wherein a first material having an index of refraction (n core ) is selected for the core and ridges, and a second material having an index of refraction (n liner ) is selected for the liner layer, wherein the first and second materials are selected to provide a first difference in the index of refraction sufficient to provide a contrast therebetween; and
depositing an amorphous or crystalline cover layer on the liner layer, wherein a third material is selected for the amorphous or crystalline cover layer having an index of refraction (n cover ) to provide a second difference in the index of refraction between the second material and the third material, and the third material is not the same as the first material.

2. The method of claim 1 , wherein the grating comprises at least a portion of a waveguide.

3. The method of claim 2 , wherein the optical waveguide is at least one of a distributed Bragg reflectors (DBRs) or a distributed Bragg deflectors (DBDs).

4. The method of claim 2 , wherein the optical waveguide is defined further as comprising at least two ECS gratings to make an edge-emitting DBR laser; one ECS grating and one regular DBR grating to make an edge-emitting DBR laser; two ECS gratings with a straight ECS outcoupler grating to make a surface-emitting laser; ECS grating and one regular DBR grating with a straight ECS outcoupler grating to make a surface-emitting laser; two ECS gratings with a “fan-out” ECS outcoupler grating to make a surface-emitting laser; one ECS grating and one regular DBR grating with a “fan-out” ECS outcoupler grating to make a surface-emitting laser; two ECS gratings with a standard grating outcoupler grating to make a surface-emitting laser; one ECS grating and one regular DBR grating with a standard grating outcoupler grating to make a surface-emitting laser; one or more ECS grating output couplers with low back reflection on both ends to make a surface-normal coupled semiconductor optical amplifier (SOA) or optical gain block; or one or more ECS gratings or regular DBR gratings configures as a mirror with high reflectivity and another ECS grating as an output coupler to make a surface-emitting reflective semiconductor optical amplifier (RSOA) or an optical gain block; a hybrid external cavity laser and tunable laser using SOA or RSOA with ECS grating output couplers integrated with a waveguide or free space wavelength control optics; or an enhanced grating for high density and low loss integration of III/V laser sources for silicon photonic interconnects.

5. The method of claim 2 , wherein the optical waveguide is defined further as comprising a non-grating transition waveguide, wherein the non-grating transition waveguide comprises:
a. a high index cover layer or a low index cover layer that converts a high loss discontinuity between the waveguide and the transition waveguide to a low loss discontinuity,
b. a high index cover layer or a low index cover layer that converts a high loss discontinuity between the waveguide and the transition waveguide to a low loss discontinuity with a second contrasting cover layer;
c. a tapered waveguide; or
d. an inverse-tapered waveguide.

6. The method of claim 1 , wherein the grating is defined further as comprising on at least one of:
a bottom of the one or more grooves;
one or more sidewalls of the ridges;
a top on the ridges;
two or more liner layers in the grooves; or
one or more sidewalls of the ridges that do not have a top.

7. The method of claim 6 , wherein the liner layer selected from one or more of the following optional configurations:
(a) the liner layer is not contiguous;
(b) the liner layer is disposed on a first sidewall, a second sidewall or both the first and second sidewalls of the ridges;
(c) the liner layer is defined further as one or more liner layers that are contiguous and that follow the contour of the ridges and the grooves;
(d) the liner layer is not contiguous, wherein the liner layer is defined further as being substantially parallel to a bottom of the one or more grooves, and the non-contiguous layers are separated by one or more amorphous or crystalline cover layers;
(e) the liner layer is defined further as two or more liner layers that are contiguous and that follow the contour of the ridges, and each of the two or more liner layers are separated by one or more amorphous or crystalline cover layers;
(f) the liner layer is disposed on one or more tops of the ridges, one or more grooves between the ridges, or both the top of the ridges, and the grooves between the ridges;
(g) the liner layer is disposed on a first sidewall, one or more tops of the ridges, and one or more grooves between the ridges, to provide an effective blazed grating;
(h) the liner layer is disposed on a first sidewall and one or more tops of the ridges; or
(i) the liner layer is disposed on one or more first sidewall or second sidewall of one or more waveguiding structures for grating coupling (inward or outward).

8. The method of claim 6 , wherein the ridges of the grating extend above the core layer.

9. The method of claim 6 , wherein the thickness of each of the core layer, grating liner layer, and amorphous or crystalline cover layer are varied to optimize the ratio of upward coupled radiation to downward coupled radiation or in the upwards or downwards direction.

10. The method of claim 6 , wherein the optical waveguide further comprises one or more additional grooves or ridges each with enhanced coupling strength gratings to provide a partially reflecting mirror that reduces or cancels a second-order in-plane Bragg reflection by destructive interference.

11. The method of claim 6 , wherein the optical waveguide further comprises one or more additional grooves or ridges to provide a partially reflecting mirror that reduces or cancels a second-order in-plane Bragg reflection by destructive interference.

12. The method of claim 6 , wherein the optical waveguide further comprises one or more additional grooves or ridges that are not covered by at least one of the liner layer or amorphous or crystalline cover layer to provide a partially reflecting mirror that reduces or cancels a second-order in-plane Bragg reflection by destructive interference.

13. The method of claim 6 , wherein the grating period is adapted for use with wavelengths in the range of 0.1 to 0.4, 0.4 to 1.0, 0.5 to 1.1, 0.6 to 1.1, and greater than 1.1.

14. The method of claim 6 , wherein the selection of the materials for the ridges is adapted for use with wavelengths in the range of 0.1 to 0.4, 0.4 to 1.0, 0.5 to 1.1, 0.6 to 1.1, and greater than 1.1.

15. The method of claim 6 , wherein the core and the ridges are unitary.

16. The method of claim 1 , wherein the liner layer is disposed on a high index contrast Si/SiO 2 waveguide to further enhance the performance of the grating.

17. The method of claim 1 , wherein the amorphous or crystalline cover layer is selected to provide the second difference in the index of refraction between the amorphous or crystalline cover layer and the liner layer as the fi

Assignees

• Univ Southern Methodist
• Oracle Int Corp

Inventors

• Evans Gary A
• Butler Jerome K
• Kirk Jay B
• He Ruo-Hua
• Yao Jin
• Li Guoliang
• Zheng Xuezhe
• Krishnamoorthy Ashok V

Classifications

• G02B6/036

  core or cladding comprising multiple layers {(multicore optical fibres G02B6/02042; microstructured properties G02B6/02295; omniguide fibres G02B6/023)} · CPC title

• G02B2006/12176

  Etching · CPC title

• G02B6/34 Primary

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

• G02B6/132

  by deposition of thin films · CPC title

• H01S5/125

  Distributed Bragg reflector [DBR] lasers · CPC title