Variable width waveguide for mode-matching and method for making
View Patent ↗A variable width waveguide useful for mode matching between dissimilar optical waveguides and optical fibers and a method for making the same is described. In one embodiment, a tapered waveguide is etched in a substrate, a cladding material is laid over the upper surface of the substrate and within the waveguide, and the waveguide is then filled with a core material. The core material may be deposited in a single step, or in successive deposition steps.
1. An optical waveguide, comprising:
a substrate comprising an upper surface and a trench therein, wherein said trench has a varying profile along at least a part of its length;
a core material in said trench; and
a cladding material in said trench between said substrate and said core material,
wherein said core material and said cladding material have a varying profile along said at least said part of the length of said trench.
2. The optical waveguide of claim 1 , wherein said trench has a profile which tapers from a large end to a small end.
3. The optical waveguide of claim 2 , wherein said trench tapers in thickness.
4. The optical waveguide of claim 2 , wherein said trench tapers from a large width to a small width.
5. The optical waveguide of claim 2 , wherein said core material at said small end has a greater index of refraction at said upper surface than said core material at said large end.
6. The optical waveguide of claim 1 , wherein said trench comprises an input waveguide channel and a plurality of output waveguide channels.
7. The optical waveguide of claim 1 , wherein said trench has a stepped profile.
8. The optical waveguide of claim 1 , wherein said trench has a profile with periodic variations in width.
9. The optical waveguide of claim 1 , wherein the refractive index of said core material decreases in a thickness direction away from said cladding material.
10. The optical waveguide of claim 1 , wherein said substrate comprises silicon.
11. The optical waveguide of claim 10 , wherein said cladding material comprises silicon dioxide.
12. The optical waveguide of claim 1 , wherein said core material comprises silicon oxynitride.
13. The optical waveguide of claim 1 , wherein said core material comprises doped glass.
14. The optical waveguide of claim 1 , wherein said substrate comprises glass.
15. The optical waveguide of claim 14 , wherein said core material comprises successively deposited material on said cladding material, wherein each successively deposited material has a lower index of refraction than the preceding deposited material.
16. A method for forming an optical waveguide of claim 1 , said method comprising:
forming a trench in a substrate comprising an upper surface, wherein the trench has a varying profile along at least a part of its length;
locating a cladding material in the trench;
depositing a core material on the cladding material in the trench; and
planarizing the substrate to the upper surface.
17. The method of claim 16 , wherein said forming comprises:
gray-scale patterning of a photoresist;
transferring the patterning of the photoresist to the substrate surface; and
etching the patterning of the photoresist.
18. The method of claim 16 , wherein said forming comprises isotropic etching.
19. The method of claim 16 , wherein the substrate comprises silicon, said locating comprising oxidizing the cladding material.
20. The method of claim 19 , wherein said oxidizing comprises a thermal oxidation process.
21. The method of claim 16 , wherein said locating comprises covering said upper surface and said trench with a chemical vapor deposition oxide.
22. The method of claim 16 , wherein said locating comprises covering said upper surface and said trench with an oxynitride.
23. The method of claim 16 , wherein said locating comprises covering said upper surface and said trench with a doped oxide.
24. The method of claim 16 , wherein said depositing comprises successive depositions of the core material on the cladding material, wherein each successive deposited core material has a lower index of refraction than the preceding deposited core material.
25. The method of claim 16 , wherein said planarizing comprises chemical-mechanical planarizing.
26. The optical waveguide of claim 1 , wherein the trench is formed by etching away a portion of the substrate.
27. The optical waveguide of claim 1 , wherein the core material and the cladding material are coplanar with the substrate upper surface.
28. An integrated optic chip, comprising:
a substrate comprising an upper surface;
a waveguide comprising:
a trench in said substrate, said trench comprising a varying profile along at least a part of its length;
a core material in said trench; and
a cladding material in said trench between said substrate and said core material;
wherein said core material and said cladding material have a varying profile along said at least said part of the length of said trench; and
integrated optical circuits optically coupled to said waveguide.
29. The integrated optic chip of claim 28 , wherein said trench has a profile which tapers from a large end to a small end.
30. The integrated optic chip of claim 29 , wherein said trench tapers in thickness.
31. The integrated optic chip of claim 29 , wherein said trench tapers from a large width to a small width.
32. The integrated optic chip of claim 29 , wherein said core material at said small end has a greater index of refraction at said upper surface than said core material at said large end.
33. The integrated optic chip of claim 28 , wherein the refractive index of said core material decreases in a thickness direction away from said cladding material.
34. The integrated optic chip of claim 28 , wherein the trench is formed by etching away a portion of the substrate.
35. The integrated optic chip of claim 28 , wherein the core material and the cladding material are coplanar with the substrate upper surface.
36. An optical waveguide, comprising:
a substrate comprising an upper surface and a trench therein, wherein said trench has a varying profile along at least a part of its length;
a core material in said trench; and
a cladding material in said trench between said substrate and said core material,
wherein said trench tapers from a large widtyh to a small width, and wherein said core material at said small end has a greater index of refraction at said upper surface than said core material at said large end.
37. An optical waveguide, comprising:
a substrate comprising an upper surface and a trench therein, wherein said trench has a varying profile along at least a part of its length;
a core material in said trench; and
a cladding material in said trench between said substrate and said core material,
wherein said core material and said cladding material fill said trench.
38. An integrated optic chip, comprising:
a substrate comprising an upper surface;
a waveguide comprising:
a trench in said substrate, said trench comprising a varying profile along at least a part of its length;
a core material in said trench; and
a cladding material in said trench between said substrate and said core material;
wherein said core material and said cladding material fill said trench; and integrated optical circuits optically coupled to said waveguide.