Optical Coupler

• US 20180067259A1
• Filed: 09/01/2017
• Published: 03/08/2018
• Est. Priority Date: 09/02/2016
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Teng, Min, Qi, Minghao, Niu, Ben, Wirth, Justin Christopher, Kim, Sangsik, Han, Kyunghun, Xuan, Yi, Lee, Yun Jo
• Granted Patent: US 10,197,731 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/1223 high refractive index type, i.e. high-contrast waveguides
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/30 for use between fibre and thin-film device
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G02B 6/3881 using grooves to align ferrule ends
• CPC Class Codes: G02B 6/3885 Multicore or multichannel optical connectors, i.e. one single ferrule containing more than one fibre, e.g. ribbon type optical ribbon cable G02B6/4403, G02B6/448

Abstract

A semiconductor photonic device includes a substrate, facet(s), and optical coupler(s) associated with the facet(s). Each optical coupler can couple an electromagnetic field incident on the respective facet towards the substrate as the electromagnetic field proceeds into the semiconductor photonic device. In some examples, each coupler has waveguides extending in a longitudinal direction and at least partly encapsulated within corresponding cladding layers. A first waveguide extends farther from the facet in the longitudinal direction than does a second waveguide. The second waveguide is located farther above the silicon substrate than is the first waveguide. The coupler can include a stack of waveguide assemblies. A lower waveguide assembly can include one waveguide. An intermediate or upper waveguide assembly can include multiple waveguides. In some examples, at least one waveguide tapers along its length.

Claims

1. An optical coupler, comprising:

a semiconductor substrate;

a first cladding layer arranged over the semiconductor substrate and having a relatively lower refractive index; and

a plurality of waveguide assemblies arranged in a stack over the first cladding layer, the plurality of waveguide assemblies comprising;

a lower waveguide assembly arranged over the first cladding layer and comprising;

a lower cladding layer having a relatively lower refractive index; and

a tapered lower waveguide at least partly encapsulated in the lower cladding layer and having a relatively higher refractive index;

at least one intermediate waveguide assembly arranged over a preceding waveguide assembly of the plurality of waveguide assemblies, each intermediate waveguide assembly comprising;

a respective cladding layer having a relatively lower refractive index; and

at least one intermediate waveguide at least partly encapsulated in the respective cladding layer and having a relatively higher refractive index; and

an upper waveguide assembly arranged over an uppermost of the at least one intermediate waveguide assembly, the upper waveguide assembly comprising;

an upper cladding layer having a relatively lower refractive index; and

at least two upper waveguides spaced apart laterally, each of the at least two upper waveguides at least partly encapsulated in the upper cladding layer and having a relatively higher refractive index.

2. The optical coupler according to claim 1, wherein:

the semiconductor substrate comprises crystalline silicon or a III-V semiconductor;

the first cladding layer comprises buried oxide;

the respective cladding layers of the at least one intermediate waveguide assembly comprise silicon oxide;

the intermediate waveguide comprises silicon nitride;

or

the at least two upper waveguides comprise silicon nitride.

3. The optical coupler according to claim 1, further comprising an active unit connected with the lower waveguide.

4. The optical coupler according to claim 1, wherein the at least one intermediate waveguide assembly comprises at least:

a first intermediate waveguide assembly comprising at most two intermediate waveguides of the corresponding at least one intermediate waveguide; and

a second intermediate waveguide assembly arranged over the first intermediate waveguide assembly and comprising at least three intermediate waveguides of the corresponding at least one intermediate waveguide.

5. The optical coupler according to claim 1, wherein the at least one intermediate waveguide assembly comprises at least two intermediate waveguide assemblies, each comprising at least three intermediate waveguides of the corresponding at least one intermediate waveguide.

6. The optical coupler according to claim 1, wherein at least a first waveguide of the at least one intermediate waveguide or of the at least two upper waveguides tapers along a length of the first waveguide.

7. The optical coupler according to claim 1, wherein at least a first waveguide of the at least one intermediate waveguide or of the at least two upper waveguides approaches at least a second waveguide of the at least two intermediate waveguides or of the at least two upper waveguides along a length of the first waveguide.

8. The optical coupler according to claim 1, wherein at least a first waveguide of the lower waveguide, the at least one intermediate waveguide, or the at least two upper waveguides comprises at least two taper sections having respective, different rates of width taper as a function of distance along a longitudinal axis of the first waveguide.

9. The optical coupler according to claim 1, wherein:

the lower waveguide comprises a first taper section, followed by a first non-taper section, followed by a second taper section along a longitudinal axis of the lower waveguide;

the at least one intermediate waveguide assembly comprises a first intermediate waveguide assembly arranged over the lower waveguide assembly and comprising a first intermediate waveguide;

the first intermediate waveguide comprises a second non-taper section, followed by a third taper section, followed by a third non-taper section along a longitudinal axis of the first intermediate waveguide;

the first taper section and the second non-taper section are intersected by a first line substantially perpendicular to the longitudinal axis of the lower waveguide;

the first non-taper section and the third taper section are intersected by a second line substantially parallel to the first line and spaced apart from the first line; and

the second taper section and the third non-taper section are intersected by a third line substantially parallel to the first line and spaced apart from the first line and from the second line.

10. The optical coupler according to claim 1, wherein the lower waveguide has a higher index of refraction than at least one of the intermediate waveguides.

11. An integrated circuit comprising:

a substrate;

a plurality of layers arranged over the substrate and configured to define;

a facet at an edge of the integrated circuit; and

an optical coupler extending away from the facet at least in a longitudinal direction;

wherein;

the optical coupler comprises a plurality of waveguides, each at least partly encapsulated within a corresponding cladding layer;

a first waveguide of the plurality of waveguides extends farther from the facet in the longitudinal direction than does a second waveguide of the plurality of waveguides; and

the second waveguide is located farther above the silicon substrate than is the first waveguide.

12. The integrated circuit according to claim 11, wherein the waveguides of the plurality of waveguides have higher refractive indices than the corresponding cladding layers.

13. The integrated circuit according to claim 11, further comprising an active unit arranged over the substrate, wherein the optical coupler is disposed at least partly between the facet and the active unit.

14. The integrated circuit according to claim 13, further comprising a processor operatively coupled to the active unit(s) to at least transmit or receive data.

15. The integrated circuit according to claim 13, wherein:

the device further comprises a plurality of active units, the plurality of active units comprising the active unit;

the plurality of layers are further configured to define;

a plurality of facets at the edge of the integrated circuit, the plurality of facets comprising the facet; and

a plurality of optical couplers disposed at least partly between respective facets of the plurality of facets and respective active units of the plurality of active units, the plurality of optical couplers comprising the optical coupler;

each optical coupler of the plurality of optical couplers defines a respective longitudinal axis; and

each optical coupler of the plurality of optical couplers comprises;

a first waveguide arranged relatively closer to the respective active unit in the longitudinal direction and relatively closer to the substrate; and

a second waveguide arranged relatively farther from the respective active unit in the longitudinal direction and relatively farther from to the substrate.

16. The integrated circuit according to claim 15, wherein:

the plurality of layers comprises a first layer and a second layer;

the first layer is arranged at least partly between the substrate and the second layer;

the respective first waveguides of the plurality of optical couplers are arranged in the first layer; and

the respective second waveguides of the plurality of optical couplers are arranged in the second layer.

17. An assembly comprising:

a semiconductor photonic device having;

a substrate;

a plurality of facets; and

a plurality of optical couplers associated with respective facets of the plurality of facets; and

a plurality of single-mode optical fibers disposed in a splice configuration with respect to respective facets of the plurality of facets;

wherein each optical coupler of the plurality of optical couplers comprises means for coupling an electromagnetic field incident on the facet towards the substrate as the electromagnetic field proceeds into the semiconductor photonic device.

18. The assembly according to claim 17, further comprising a V-groove array configured to retain the single-mode optical fibers in position with respect to the respective facets.

19. The assembly according to claim 17, wherein each optical coupler comprises:

a respective first waveguide disposed over the substrate; and

a respective second waveguide disposed over the substrate, the respective second waveguide being farther from the substrate than the respective first waveguide and extending closer to the respective facet than the respective first waveguide.

20. The assembly according to claim 19, wherein the respective first waveguides and the respective second waveguides:

are at least partly encapsulated in corresponding cladding layers; and

have respective indices of refraction that are higher than respective indices of refraction of the corresponding cladding layers.