Embedded mode converter

• US 20040037497A1
• Filed: 12/05/2002
• Published: 02/26/2004
• Est. Priority Date: 08/20/2002
• Status: Active Grant

• Current Assignee: Enablence Canada, Inc. (Enablence Technologies Incorporated), LNL Technologies, Inc.
• Original Assignee: LNL Technologies, Inc.
• Inventors: Lee, Kevin K.
• Granted Patent: US 6,870,987 B2
• Time in Patent Office: Days
• 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 6/132 by deposition of thin films

Abstract

An optical mode transformer. The optical mode transformer features a low index core, a high index core having a first tapered region, with the high index core embedded within the low index core and with the low index core serving as a cladding for a waveguide defined by the high index core embedded in the low index core, and a cladding layer surrounding the low index core, with the cladding layer including one or more materials with different refractive indices than those of the low index core and high index core.

Claims

1. An optical mode transformer, comprising:

a low index core;

a high index core having a first tapered region, wherein the high index core is embedded within the low index core and wherein the low index core serves as a cladding for a waveguide defined by the high index core embedded in the low index core; and

a cladding layer surrounding the low index core, wherein the cladding layer is composed of one or more materials with different refractive indices than those of the low index core and high index core, wherein a first channel-like mode defined by the low index core and cladding layer gradually transforms into a second channel-like mode defined by the high index core embedded within the low index core.

2. The optical mode transformer of claim 1, wherein the low index core increases in dimension while embedding the high index core.

3. The optical mode transformer of claim 2, wherein the dimension of the low index core is increased to a multi-mode waveguide dimension.

4. The optical mode transformer of claim 2, wherein the dimension of the low index core is increased to a slab waveguide region that forms the cladding.

5. The optical mode transformer of claim 1, wherein the low index core is connected to a slab waveguide.

6. The optical mode transformer of claim 1, wherein a first region of the optical mode transformer is the waveguide defined by the high index core embedded in the low index core and a second region is defined by the low index core not embedding the high index core.

7. The optical mode transformer of claim 6, wherein the first tapered region forms the beginning of the waveguide defined by the high index core embedded in the low index core, and wherein the low index core contains a taper forming a decreased dimension around the high index core in the beginning of the waveguide having the high index core.

8. The optical mode transformer of claim 7, wherein the low index core increases in dimension after the taper to form the cladding.

9. The optical mode transformer of claim 6, wherein the first region is a high index difference waveguide and the second region forms a low index difference waveguide.

10. The optical mode transformer of claim 6, wherein the second region has a peak optical intensity at a position in the low index core, wherein the position of the peak optical intensity is defined in a cross-section perpendicular to a propagation direction of light.

11. The optical mode transformer of claim 10, wherein the first region has a peak optical intensity at a position in the high index core.

12. The optical mode transformer of claim 1, wherein the index of refraction of the low index core is relatively lower than the index of refraction of the high index core.

13. The optical mode transformer of claim 1, wherein the index of refraction of the low index core is slightly higher than the index of refraction of the cladding layer.

14. The optical mode transformer of claim 1, wherein the index of refraction of the high index core is substantially higher than the indices of refraction of the low index core and the cladding layer.

15. The optical mode transformer of claim 1, wherein a propagating optical mode is transformed in size, shape, and speed as it propagates between the low index core and the high index core.

16. The optical mode transformer of claim 1, wherein a propagating optical mode can propagate bi-directionally between the low index core and the high index core.

17. The optical mode transformer of claim 1, wherein a propagating optical mode can propagate bi-directionally between the low index core surrounded by the cladding layer and the high index core surrounded by the low index core.

18. The optical mode transformer of claim 1, wherein the first tapered region of the high index core provides an effective refractive index change to a propagating optical mode.

19. The optical mode transformer of claim 1, wherein the first tapered region of the high index core is continuous or linear.

20. The optical mode transformer of claim 1, wherein the first tapered region of the high index core is segmented or non-linear.

21. The optical mode transformer of claim 1, wherein the low index core and the high index core are made by a combination of layer creation and etching processes, wherein the layer creation process is one of a deposition process and a wafer-bonding process.

22. The optical mode transformer of claim 21, wherein a portion of the low index core is deposited before the layer creation and etching of the high index core and the remaining portion of the low index core is deposited after the layer creation and etching of the high index core.

23. The optical mode transformer of claim 21, wherein the low index core is patterned by etching after the layer creation and etching of the high index core.

24. The optical mode transformer of claim 1, wherein the high index core is made from a high refractive index material with a refractive index significantly higher than that of silica.

25. The optical mode transformer of claim 1, wherein the high index core is made from a nitrogen-containing compound.

26. The optical mode transformer of claim 25, wherein the nitrogen-containing compound is selected from Silicon Oxynitride, Silicon Nitride, and Silicon-rich Silicon nitride.

27. The optical mode transformer of claim 1, wherein the high index core is made from one of doped silica and Silicon.

28. The optical mode transformer of claim 1, wherein the low index core is made from one of undoped silica, doped silica, and silicon oxynitride.

29. The optical mode transformer of claim 1, wherein the cladding layer is made from one of undoped silica, doped silica, and silicon oxynitride.

30. An optical device, comprising:

two or more optical mode transformers, with each optical mode transformer comprising;

a low index core;

a high index core having a first tapered region, wherein the high index core is embedded within the low index core and wherein the low index core serves as a cladding for a waveguide defined by the high index core embedded in the low index core; and

a cladding layer surrounding the low index core, wherein the cladding layer is composed of one or more materials with different refractive indices than those of the low index core and high index core, wherein a first channel-like mode defined by the low index core and cladding layer gradually transforms into a second channel-like mode defined by the high index core embedded within the low index core.

31. The optical device of claim 30, wherein two or more of the low index cores of the optical mode converters are connected to a single slab waveguide region that forms the cladding for the waveguides defined by the high index cores embedded in the low index cores.

32. The optical device of claim 31, wherein each optical mode transformer has a first region that is the waveguide defined by the high index core embedded in the low index core and a second region that is defined by the low index core not embedding the high index core.

33. The optical mode transformer of claim 32, wherein, for each optical mode transformer, the first tapered region forms the beginning of the waveguide defined by the high index core embedded in the low index core, and wherein the low index core contains a taper forming a decreased dimension around the high index core in the beginning of the waveguide having the high index core.

34. The optical device of claim 33, wherein, for each optical mode transformer, the low index core increases in dimension after the taper to form the cladding.

35. A dielectric waveguide optical mode transformer, comprising:

a first dielectric channel waveguide including a first core material surrounded by a cladding layer;

a second dielectric channel waveguide including a second core material having a first tapered region forming one end of the second dielectric channel waveguide, the second core material being embedded within the first core material, wherein the first core material tapers outward to increase in dimension and acts as a cladding for the second dielectric channel waveguide having the second core material.

36. The dielectric waveguide optical mode transformer of claim 35, wherein the first dielectric channel waveguide is a low index difference waveguide and the second dielectric channel waveguide is a high index difference waveguide.

37. The dielectric waveguide optical mode transformer of claim 36, wherein the first core material contains a taper decreasing in dimension in a vicinity of the first tapered region of the second core material before the first core material tapers outward.

38. A method of bi-directionally coupling a propagating optical mode between a low index difference waveguide and a high index difference waveguide, comprising:

providing a low index core;

providing a high index core having a first tapered region, wherein the high index core is embedded within the low index core and wherein the low index core serves as a cladding for the high index difference waveguide defined by the high index core embedded in the low index core;

providing a cladding layer surrounding the low index core to form the low index difference waveguide, wherein the cladding layer is composed of one or more materials with different refractive indices than those of the low index core and high index core; and

introducing a propagating optical mode into one of the low index difference waveguide and the high index difference waveguide, wherein the propagating optical mode is gradually transformed between that of a first channel-like mode defined by the low index difference waveguide and that of a second channel-like mode defined by the high index difference waveguide.

39. A dielectric waveguide optical mode transformer, comprising:

a first dielectric channel waveguide including a low index core surrounded by a cladding layer;

a second dielectric channel waveguide including a high index core embedded at least partially within the low index core, wherein the low index core acts as a cladding for the second dielectric channel waveguide having the high index core; and

a transformer region, the transformer region being between the first dielectric channel waveguide and the second dielectric channel waveguide, wherein, in the transformer region, the high index core extends from the second dielectric channel waveguide and tapers downward to decrease in dimension so that the high index core has one end within the transformer region near the first dielectric channel waveguide, and wherein the low index core material extends from the first dielectric channel waveguide into the transformer region, embeds the high index core, and tapers outward to increase in dimension near the second dielectric channel waveguide.

40. The dielectric waveguide optical mode transformer of claim 39, wherein, in the second dielectric channel waveguide, the high index core is bound on top and bottom sides by the low index core.

41. The dielectric waveguide optical mode transformer of claim 40, wherein, in the second dielectric channel waveguide, the high index core is not bound on left and right sides by the low index core, but is instead bound on the left and right sides by the cladding layer.