Waveguide crossing

Patent metadata

Field	Value
Publication number	US-9709738-B1
Application number	US-201615067443-A
Country	US
Kind code	B1
Filing date	Mar 11, 2016
Priority date	Mar 11, 2016
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A waveguide crossing includes a first waveguide and a second waveguide intersecting the first waveguide such that a gap equal to a width of the second waveguide is formed in the first waveguide, the second waveguide having a centerline defining a plane of symmetry. The first waveguide has a first waveguide section through which a single optical mode propagates, followed by a first non-adiabatic diverging taper, followed by a second waveguide section wider than the first waveguide section through which two even-order optical modes propagate, followed by a second non-adiabatic diverging taper, followed by a third waveguide section wider than the second waveguide section through which three even-order optical modes propagate. The three even-order modes synthesize to form a quasi-Gaussian beam that self-replicates symmetrically across the gap, thereby providing a low-loss waveguide crossing useful for photonic switching.

First claim

The invention claimed is:

1. A waveguide crossing comprising:
a first waveguide;
a second waveguide intersecting the first waveguide such that a gap equal to a width of the second waveguide is formed in the first waveguide;
wherein the first waveguide comprises a first waveguide section through which a single optical mode propagates, followed by a first non-adiabatic diverging taper, followed by a second waveguide section wider than the first waveguide section, through which two even-order optical modes propagate, followed by a second non-adiabatic diverging taper, followed by a third waveguide section wider than the second waveguide section through which three even-order optical modes propagate; and
wherein the first waveguide further comprises, downstream of the gap, a fourth waveguide section, followed by a first non-adiabatic converging taper, followed by a fifth waveguide section narrower than the fourth waveguide section, followed by a second non-adiabatic converging taper, followed by a sixth waveguide section narrower than the fifth waveguide section.

2. The waveguide crossing of claim 1 wherein the second waveguide has a centerline defining a plane of symmetry, wherein the fourth and fifth waveguide sections are symmetrical with respect to the plane of symmetry to the third and second waveguide sections, respectively, and wherein the first and second converging non-adiabatic tapers are symmetrical with respect to the plane of symmetry to the second and first diverging non-adiabatic tapers, respectively.

3. The waveguide crossing of claim 1 wherein the first and second non-adiabatic diverging tapers and the second and third waveguide sections are configured so that the three even-order optical modes interfere at a first interface between the third waveguide section and the gap to form a converging optical beam having a beam waist in the gap.

4. The waveguide crossing of claim 1 wherein the second waveguide has a centerline defining a plane of symmetry, and wherein the first and second non-adiabatic diverging tapers and the second and third waveguide sections are configured so that the three even-order modes interfere at a first interface between the third waveguide section and the gap to form a converging quasi-Gaussian beam across the gap, wherein the quasi-Gaussian beam is substantially symmetrical with respect to the plane of symmetry.

5. The waveguide crossing of claim 1 wherein the first to sixth waveguide sections have constant widths.

6. The waveguide crossing of claim 1 wherein the first waveguide section comprises an adiabatic taper that widens towards the first non-adiabatic diverging taper.

7. The waveguide crossing of claim 1 wherein the second waveguide section comprises an adiabatic taper that widens towards the second non-adiabatic diverging taper.

8. The waveguide crossing of claim 1 wherein the third waveguide section comprises an adiabatic taper that widens towards the gap.

9. The waveguide crossing of claim 1 wherein the second waveguide section has a length L A selected to adjust a phase offset between the two even-order optical modes.

10. The waveguide crossing of claim 1 wherein the third waveguide section has a length L B selected to adjust a phase offset between the three even-order optical modes.

11. The waveguide crossing of claim 1 wherein the second waveguide comprises a first waveguide section through which a single optical mode propagates, followed by a first non-adiabatic diverging taper, followed by a second waveguide section wider than the first waveguide section, through which two even-order optical modes propagate, followed by a second non-adiabatic diverging taper, followed by a third waveguide section wider than the second waveguide section through which three even-order optical modes propagate; and
wherein the second waveguide further comprises, downstream of the gap, a fourth waveguide section, followed by a first non-adiabatic converging taper, followed by a fifth waveguide section narrower than the fourth waveguide section, followed by a second non-adiabatic converging taper, followed by a sixth waveguide section narrower than the fifth waveguide section.

12. A method of propagating light across a waveguide crossing having a first waveguide intersecting a second waveguide such that a gap equal to a width of the second waveguide is formed in the first waveguide, the method comprising:
propagating light having a single optical mode through a first waveguide section of the first waveguide;
transforming the light through a first non-adiabatic diverging taper from the single optical mode to two even-order optical modes;
propagating the light having the two even-order optical modes through a second waveguide section wider than the first waveguide section;
transforming the light through a second non-adiabatic diverging taper from the two even-order optical modes to three even-order optical modes;
propagating the light through a third waveguide section wider than the second waveguide section to the gap where the three modes interfere to form a beam profile that self-replicates across the gap.

13. The method of claim 12 further comprising:
propagating the light having the three even-order optical modes through a fourth waveguide section;
transforming the light through a first non-adiabatic converging taper from the three even-order optical modes to two even-order optical modes;
propagating the light having the two even-order optical modes through a fifth waveguide section narrower than the fourth waveguide section;
transforming the light through a second non-adiabatic converging taper from the two even-order optical modes to a single optical mode;
propagating the light through a sixth waveguide section narrower than the fifth waveguide section.

14. The method of claim 13 further comprising propagating the light through an adiabatic taper in the first waveguide section that widens from a single-mode waveguide to the first waveguide section.

15. The method of claim 14 further comprising propagating the light through adiabatic tapers in the second and third waveguide sections.

Assignees

• Dumais Patrick
• Huawei Tech Co Ltd

Inventors

• Dumais Patrick

Classifications

• G02B6/2813

  based on multimode interference effect, i.e. self-imaging · CPC title

• G02B6/1228

  Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305) · CPC title

• G02B6/125 Primary

  Bends, branchings or intersections · CPC title

• G02B6/14

  Mode converters · CPC title