Optical couplers with diagonal light transfer

1. A structure for an optical coupler, the structure comprising:

a first waveguide core having a first tapered section; and

a second waveguide core having a second tapered section positioned adjacent to the first tapered section of the first waveguide core, the second tapered section positioned with a first lateral offset in a lateral direction relative to the first tapered section, and the second tapered section positioned with a first vertical offset in a vertical direction relative to the first tapered section.

2. The structure of claim 1 wherein the first tapered section includes a first longitudinal axis and a first plurality of segments positioned with a first spaced arrangement along the first longitudinal axis.

3. The structure of claim 2 wherein the first plurality of segments define a subwavelength grating.

4. The structure of claim 2 wherein the second tapered section includes a second longitudinal axis and a second plurality of segments positioned with a second spaced arrangement along the second longitudinal axis.

5. The structure of claim 1 wherein the second tapered section includes a longitudinal axis and a plurality of segments positioned with a spaced arrangement along the longitudinal axis.

6. The structure of claim 5 wherein the plurality of segments define a subwavelength grating.

7. The structure of claim 1 further comprising:

a third waveguide core having a third tapered section positioned adjacent to the second tapered section, the third tapered section positioned with a second lateral offset in the lateral direction relative to the second tapered section of the second waveguide core, and the third tapered section positioned with a second vertical offset in the vertical direction relative to the second tapered section of the second waveguide core.

8. The structure of claim 7 wherein the first tapered section and the second tapered section are non-overlapping due to the first lateral offset, and the second tapered section and the third tapered section are non-overlapping due to the second lateral offset.

9. The structure of claim 1 wherein the first waveguide core comprises silicon, and the second waveguide core comprises silicon nitride.

10. The structure of claim 1 further comprising:

a first dielectric layer arranged to separate the first tapered section from the second tapered section,

wherein the first tapered section is embedded in the first dielectric layer.

11. The structure of claim 1 wherein the first tapered section and the second tapered section have a non-overlapping relationship due to the first lateral offset.

12. The structure of claim 1 wherein the first waveguide core includes an input section and a terminator, the first tapered section is arranged between the input section and the terminator, the second waveguide core includes an output section connected to the second tapered section, and the output section includes a plurality of bends arranged to laterally displace the second waveguide core away from the first waveguide core.

13. The structure of claim 1 wherein the first waveguide core includes an input section and a first output section, the first tapered section is arranged between the input section and the first output section, the second waveguide core includes a second output section connected to the second tapered section, and the first output section and the second output section each include a plurality of bends arranged to laterally displace the second waveguide core away from the first waveguide core.

14. The structure of claim 1 wherein the first tapered section has a first longitudinal axis and narrows in width in a first direction along the first longitudinal axis, the second tapered section has a second longitudinal axis aligned parallel to the first longitudinal axis and narrows in width in a second direction along the second longitudinal axis, and the first direction is opposite to the second direction.

15. A method of forming a structure for an optical coupler, the method comprising:

forming a first waveguide core that includes a first tapered section; and

forming a second waveguide core that includes a second tapered section positioned adjacent to the first tapered section,

wherein the second tapered section is positioned with a lateral offset in a lateral direction relative to the first tapered section of the first waveguide core, and the second tapered section is positioned with a vertical offset in a vertical direction relative to the first tapered section of the first waveguide core.

16. The method of claim 15 wherein the first waveguide core is formed by patterning a first layer comprised of a semiconductor material, and the second waveguide core is formed by patterning a second layer comprised of a dielectric material.

17. The method of claim 15 wherein forming the first waveguide core that includes the first tapered section comprises:

forming a plurality of segments positioned with a spaced arrangement to define the first tapered section.

18. The method of claim 15 wherein forming the second waveguide core that includes the second tapered section positioned adjacent to the first tapered section comprises:

forming a plurality of segments positioned with a spaced arrangement to define the second tapered section.

19. The method of claim 15 wherein the first tapered section and the second tapered section have a non-overlapping relationship due to the lateral offset.

20. The structure of claim 1 wherein the first tapered section is located adjacent to the second tapered section over a coupling region, and the first lateral offset and the first vertical offset diagonally position the first tapered relative to the second tapered section such that light is evanescently coupled in a diagonal direction across the coupling region between the first tapered section and the second tapered section.