Adiabatic optical coupler for direct SOI to interposer coupling

1. An adiabatic optical coupler comprising:

a top tapered region that includes a top taper having two top tapered sides that taper from a first end region to a top tip region, the top taper having a first length; and

a bottom tapered region under the top tapered region, wherein the bottom tapered region includes a bottom taper having two bottom tapered sides that taper from the first end region to a bottom tip region, the bottom taper having a second length that is longer than the first length,

wherein a first stage including the top and bottom tapered regions that extends from the first end region to about the top tip region has a first effective index gradient that changes as a top width of the top taper changes, and

wherein a second stage including the bottom tapered region that extends from the top tip region to the bottom tip region has a second effective index gradient that changes as a bottom width of the bottom taper changes.

2. The adiabatic optical coupler of claim 1 , wherein the top tapered region is integrated with the bottom tapered region as a unitary optically transmissive body.

3. The adiabatic optical coupler of claim 1 , wherein the top tapered region is a body coupled with a body the bottom tapered region.

4. The adiabatic optical coupler of claim 1 , wherein the top tip region terminates in a first blunt width; and wherein the bottom tip region terminates in a second blunt width being the same as or different from the first blunt width.

5. The adiabatic optical coupler of claim 1 , wherein the first effective index gradient is different from the second effective index gradient.

6. The adiabatic optical coupler of claim 1 , wherein the top taper is over a portion of the bottom taper adjacent to the first end region, and another portion of the bottom taper adjacent to the bottom tip region is devoid of the top taper thereover.

7. An optically coupled system, comprising:

the adiabatic optical coupler of claim 1 ; and

an interposer optically coupled with the adiabatic optical coupler.

8. A method of propagating light through the adiabatic optical coupler to the interposer of the optically coupled system of 7 , the method comprising:

introducing light into the first end region of the adiabatic optical coupler;

propagating the light through the top tapered region and bottom tapered region;

transitioning at least a portion of the light from the top tapered region to the bottom tapered region;

propagating the light through the bottom tapered region; and

transitioning the light from the bottom tapered region to the interposer.

9. A method of manufacturing the adiabatic optic coupler of claim 1 , the method comprising:

forming an optically transmissive body;

shaping a portion of a top region of the optically transmissive body to form the top tapered region; and

shaping a portion of a bottom region of the optically transmissive body to form the bottom tapered region.

10. An optical system comprising:

the optically coupled system of claim 7 ; and

a photonic integrated circuit (PIC) optically coupled to the adiabatic optical coupler.

11. An adiabatic optical coupler comprising:

a tapered region that includes a taper having two tapered sides that taper from an end region to a tip region; and

a sub-wavelength grating (SWG) optically coupled with the tip region.

12. The adiabatic optical coupler of claim 11 , further comprising a first gap between a blunt tip end of the tip region and a first pillar of the SWG, and wherein the SWG includes a pillar set that includes at least two spaced apart pillars with a second gap between each pillar.

13. The adiabatic optical coupler of claim 12 , wherein the pillar set includes at least one rectangular pillar having a rectangular cross-sectional profile in a width, height and/or length planes.

14. The adiabatic optical coupler of claim 12 , wherein the pillar set includes at least one tapered pillar having a trapezoidal cross-sectional profile in the width and length plane.

15. The adiabatic optical coupler of claim 14 , wherein the at least one tapered pillar has a rectangular cross-sectional profile in the height and length plane and/or width and height plane.

16. The adiabatic optical coupler of claim 11 , further comprising:

a first stage that includes the tapered region; and

a second stage that includes the SWG,

wherein the first stage has a first effective index gradient that changes as a first width of the taper changes; and

wherein the second stage has a second effective index gradient that changes as a second width of the SWG changes.

17. The adiabatic optical coupler of claim 16 , wherein the first effective index gradient is different from the second effective index gradient.

18. An optically coupled system comprising:

the adiabatic optical coupler of claim 11 ; and

an interposer optically coupled with the adiabatic optical coupler.

19. A method of propagating light through the optically coupled system of claim 18 , the method comprising:

introducing light into the end region of the adiabatic optical coupler;

propagating the light through the tapered region;

transitioning the light from the tapered region to the SWG;

propagating the light through the SWG; and

transitioning the light from the SWG to the interposer.

20. A method of manufacturing the adiabatic optic coupler of claim 11 , the method comprising:

forming an optically transmissive body;

shaping the optically transmissive body to form the tapered region; and

shaping a portion of the tapered region of the optically transmissive body to from the pillar set.

21. An adiabatic optical coupler comprising:

a top tapered region that includes a top taper having two top tapered sides that taper from a first end region to a top tip region, the top taper having a first length;

a bottom tapered region under the top tapered region, wherein the bottom tapered region includes a bottom taper having two bottom tapered sides that taper from the first end region to a bottom tip region, the bottom taper having a second length that is longer than the first length; and

a sub-wavelength grating (SWG) optically coupled with the bottom tip region.

22. The adiabatic optical coupler of claim 21 , wherein the adiabatic optical coupler includes:

a first stage that includes the top tapered region and bottom tapered region that extends from the first end region to about the top tip region;

a second stage that includes the bottom tapered region that extends from the top blunt tip end to the bottom tip region; and

a third stage includes the SWG, wherein: the first stage has a first effective index gradient that changes as a first width of the top taper changes; the second stage has a second effective index gradient that changes as a second width of the bottom taper changes; and the third stage has a third effective index gradient that changes as a third width of the changes.

23. The adiabatic optical coupler of claim 21 , wherein the top taper is over a portion of the bottom taper adjacent to the first end region, and another portion of the bottom taper adjacent to the bottom tip region is devoid of the top taper there over.

24. The adiabatic optical coupler of claim 23 , further comprising a gap between a bottom blunt tip end of the bottom tip region and a first pillar of the SWG.

25. The adiabatic optical coupler of claim 21 , wherein the SWG includes a pillar set, wherein the pillar set includes a plurality of spaced apart pillars with gaps between adjacent pillars.

26. The adiabatic optical coupler of claim 25 , wherein the pillar set includes at least one rectangular pillar having a rectangular cross-sectional profile in a width, height and/or length planes.

27. The adiabatic optical coupler of claim 25 , wherein the pillar set includes at least one tapered pillar having a trapezoidal cross-sectional profile in the width and length plane, wherein the at least one tapered pillar has a rectangular cross-sectional profile in the height and length plane and/or width and height plane.

28. The adiabatic optical coupler of claim 25 , wherein each gap is air, an optically transmissive material, includes SiN, or includes silicon dioxide.

29. The adiabatic optical coupler of claim 25 , wherein each pillar of the pillar set has a smaller width than a preceding pillar from the bottom blunt tip end to an opposite pillar.

30. A method of manufacturing the adiabatic optic coupler of claim 21 , the method comprising:

forming an optically transmissive body;

shaping a portion of a top region of the optically transmissive body to form the shape of the top tapered region and to form the shape of the bottom tapered region; and

shaping a portion of the bottom tapered region of the optically transmissive body to form the SWG.

31. An optically coupled system comprising:

the adiabatic optical coupler of claim 21 ; and

an interposer optically coupled with the adiabatic optical coupler.

32. A method of propagating light through an optically coupled system of claim 31 , the method comprising:

introducing light into the end region of the adiabatic optical coupler;

propagating the light through the top tapered region and bottom tapered region;

transitioning at least a portion of the light from the top tapered region to the bottom tapered region; propagating the light through the bottom tapered region;

transitioning the light from the bottom tapered region to the SWG;

propagating the light through the SWG; and

transitioning the light from the SWG to the interposer.

33. The method of claim 32 , further comprising:

transitioning the light from the top tapered region to the bottom tapered region at a location where an effective index of refraction of the top tapered region matches an index of refraction of the bottom tapered region; and

transitioning the light from the SWG to the interposer at a location where the effective index of refraction of the SWG matches an index of refraction of the interposer.