Multimode optical coupler interfaces

• US 8,488,923 B2
• Filed: 03/29/2010
• Issued: 07/16/2013
• Est. Priority Date: 03/29/2010
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Na, Yun-Chung, Yin, Tao
• Primary Examiner(s): Peng, Charlie
• Assistant Examiner(s): Radkowski, Peter
• Application Number:
  US12/749,196
• Publication Number:
  US 20110235968A1
• Time in Patent Office: 1,205 Days
• Field of Search: 385/28, 385/14
• US Class Current: 385/28
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• CPC Class Codes: G02B 6/2808 using a mixing element which evenly distributes an input signal over a number of outputs
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide

Abstract

Optical interfaces that may be employed between large-core optical fibers and chip-scale optoelectronic devices. Described herein are couplers that improve the tolerance of misalignment when a single mode (SM) fiber is used as waveguide input. This enables the possibility of passive/automatic alignment and therefore reduces the production cost. The coupler also serves as a spot-size converter that reduces the spot size and is suitable for applications where a waveguide mode with small cross-section area is of particular importance. One such example can be a waveguide-based SiGe or III-V semiconductor photodetector in which the vertical size of its waveguide mode should be as small as few microns.

Claims

1. An multi-mode optical coupler comprising:

an input multi-mode waveguide to receive an optical signal from a single mode optical fiber;

one or more single mode output waveguides optically coupled with the input multi-mode waveguide to form a single mode waveguide array, the one or more single mode output waveguides to receive the excited multiple modes caused by fiber misalignment, wherein the widths of the single mode output waveguides are adiabatically tapered in an increasing fashion to pull dispersions of the single mode waveguides toward a low frequency side and sweep the input frequencies to transfer optical power in the multimode waveguide into the single mode waveguide array adiabatically, wherein optical couplers to couple the one or more single mode output waveguides with the input multi-mode waveguide possess horizontal mirror symmetry to categorize the waveguide modes into either even or odd parity and the multi-mode waveguide can only interact with the single-mode waveguide array among modes with the same polarity to cause a subset of normal-mode splittings.

2. The multi-mode optical coupler of claim 1 wherein the one or more single mode output waveguides is embedded within or on top of the input multi-mode waveguide.

3. The multi-mode optical coupler of claim 1 wherein the one or more single mode output waveguides comprise single mode waveguides having adiabatically tapered widths.

4. The multi-mode optical coupler of claim 1 wherein the multi-mode input waveguide is at least ten times thicker than the one or more single mode output waveguides.

5. The multi-mode optical coupler of claim 1 wherein the multi-mode input waveguide comprises a silicon (Si) optical waveguide.

6. The multi-mode optical coupler of claim 1 wherein the multi-mode input waveguide comprises an aluminum gallium arsenide (AlGaAs) waveguide.

7. The multi-mode optical coupler of claim 1 wherein the one or more single mode output waveguides comprise aluminum arsenide (AlAs) optical waveguides.

8. The multi-mode optical coupler of claim 1 wherein the one or more single mode output waveguides comprise silicon germanium (SiGe) optical waveguides.

9. The multi-mode optical coupler of claim 8 wherein the one or more SiGe single mode output waveguides have a composition of Si_xGe_1-x.

10. An optical system comprising:

a single mode optical fiber to transmit an optical signal;

an input multi-mode waveguide to receive the optical signal from the single mode optical fiber;

one or more single mode output waveguides having adiabatically tapered widths optically coupled with the input multi-mode waveguide, the one or more single mode output waveguides to receive the excited multiple modes caused by fiber misalignment, wherein the widths of the single mode output waveguides are adiabatically tapered in an increasing fashion to pull dispersions of the single mode waveguides toward a low frequency side and sweep the input frequencies to transfer optical power in the multi-mode waveguide into the single mode waveguide array adiabatically, wherein optical couplers to couple the one or more single mode output waveguides with the input multi-mode waveguide possess horizontal mirror symmetry to categorize the waveguide modes into either even or odd parity and the multi-mode waveguide can only interact with the single-mode waveguide array among modes with the same polarity to cause a subset of normal-mode splittings.

11. The optical system of claim 10 wherein the one or more single mode output waveguides is embedded within or on top of the input multi-mode waveguide.

12. The optical system of claim 10 wherein the multi-mode input waveguide is at least ten times thicker than the one or more single mode output waveguides.

13. The optical system of claim 10 further comprising one or more optoelectronic devices optically coupled with the one or more output waveguides.

14. The optical system of claim 10 wherein the multi-mode input waveguide comprises a silicon (Si) optical waveguide.

15. The optical system of claim 10 wherein the multi-mode input waveguide comprises an aluminum gallium arsenide (AlGaAs) waveguide.

16. The optical system of claim 10 wherein the one or more single mode output waveguides comprise aluminum arsenide (AlAs) optical waveguides.

17. The optical system of claim 10 wherein the one or more single mode output waveguides comprise silicon germanium (SiGe) optical waveguides.

18. The optical system of claim 17 wherein the one or more SiGe single mode output waveguides have a composition of Si_xGe_1-x.

19. A method for manufacturing a multi-mode optical coupler, the method comprising:

creating a multi-mode silicon (Si) strip waveguide on a silicon dioxide (SiO2) substrate; and

creating a plurality of silicon germanium (SiGe) single mode output waveguides on a face of the Si strip waveguide opposite the SiO2 substrate, wherein the output waveguides have adiabatically tapered widths, wherein the widths of the single mode output waveguides are adiabatically tapered in an increasing fashion to pull dispersions of the single mode waveguides toward a low frequency side and sweep the input frequencies to transfer optical power in the multi-mode Si strip waveguide into the single mode waveguide array adiabatically, wherein optical couplers to couple the one or more single mode output waveguides with the input multi-mode waveguide possess horizontal mirror symmetry to categorize the waveguide modes into either even or odd parity and the multi-mode waveguide can only interact with the single-mode waveguide array among modes with the same polarity to cause a subset of normal-mode splittings.

20. The method of claim 19 wherein the multi-mode input waveguide is at least ten times thicker than the output waveguides.

21. The method of claim 19 wherein the SiGe output waveguides have a composition of Si_xGe_1-x.

22. A method for manufacturing a multi-mode optical coupler, the method comprising:

creating a multi-mode silicon (Si) strip waveguide on a silicon dioxide (SiO2) substrate; and

creating a single silicon germanium (SiGe) output waveguide on a face of the Si strip waveguide opposite the SiO2 substrate, wherein the output waveguides have adiabatically tapered widths, wherein the widths of the single mode output waveguides are adiabatically tapered in an increasing fashion to pull dispersions of the single mode waveguides toward a low frequency side and sweep the input frequencies to transfer optical power in the multi-mode Si strip waveguide into the single mode waveguide array adiabatically, wherein optical couplers to couple the one or more single mode output waveguides with the input multi-mode waveguide possess horizontal mirror symmetry to categorize the waveguide modes into either even or odd parity and the multi-mode waveguide can only interact with the single-mode waveguide array among modes with the same polarity to cause a subset of normal-mode splittings.

23. The method of claim 22 wherein the multi-mode input waveguide is at least ten times thicker than the output waveguide.

24. The method of claim 22 wherein the SiGe output waveguides have a composition of Si_xGe_1-x.