Optical backplanes with integrated optical couplers and methods of making the same

• US 20060210213A1
• Filed: 03/15/2005
• Published: 09/21/2006
• Est. Priority Date: 03/15/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Huang, Lidu, Yokouchi, Kishio
• Granted Patent: US 7,206,472 B2
• Time in Patent Office: Days
• US Class Current: 385/14
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/43 Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections

Abstract

Optical backplanes providing integrated optical couplers to external optical fibers are disclosed, along with methods for making the same. An exemplary optical backplane has a first cladding layer disposed over the top surface of a substrate, and at least a first core body disposed over the first cladding layer, with the first core body having a first end and a second end. A material layer is disposed above the first cladding layer and the first end of the first core body, with the material layer having a top surface and a bottom surface. A focusing element is formed at the top surface of the material layer, with the focusing element being located above the first end of the first core body.

Claims

1. An optical backplane comprising:

a substrate having a top surface and a bottom surface;

a lower cladding layer disposed over the top surface of the substrate;

a first core body having a first end and a second end, at least a portion of the first core body being in contact with the lower cladding layer;

a material layer disposed above the lower cladding layer and the first end of the first core body, the material layer having a top surface and a bottom surface; and

a focusing element formed at the top surface of the material layer, the focusing element being located above the first end of the first core body.

2. The optical backplane of claim 1 wherein the focusing element comprises a lens.

3. The optical backplane of claim 2 wherein the material layer comprises a photorefractive material having an initial refractive index, and wherein the lens comprises a modified form of the photorefractive material having a refractive index that is greater than the initial refractive index.

4. The optical backplane of claim 2 wherein the material layer has a first refractive index and a recess formed at its top surface in the location of the lens, and wherein the lens is disposed in the recess and comprises a material that has a second refractive index that is different from the first refractive index.

5. The optical backplane of claim 2 wherein the lens comprises a bump on the top surface of the material layer.

6. The optical backplane of claim 5 wherein the lens comprises a material having a first refractive index, and wherein the optical backplane further comprises a cover layer disposed over the bump and at least a portion of the material layer, the cover layer having a second refractive index that is less than the first refractive index.

7. The optical backplane of claim 2 wherein the lens comprises a depression in the top surface of the material layer.

8. The optical backplane of claim 7 wherein the material layer has a first refractive index, and wherein the optical backplane further comprises a cover layer disposed over the depression and at least a portion of the material layer, the cover layer having a second refractive index that is greater than the first refractive index.

9. The optical backplane of claim 1 wherein the focusing element comprises a grating.

10. The optical backplane of claim 1 wherein the material layer comprises a photorefractive material having an initial refractive index, and wherein the grating comprises a plurality of concentric rings disposed at the top surface of the material layer, each concentric ring comprising a modified form of the photorefractive material having a refractive index that is greater than the initial refractive index.

11. The optical backplane of claim 1 wherein the grating comprises a plurality of concentric rings of material removed from the top surface of the material layer.

12. The optical backplane of claim 1 further comprising a receptacle disposed above the material layer and having a slot to receive a ribbon fiber connector, the receptacle being disposed such that its slot is located above the focusing element.

13. The optical backplane of claim 12, wherein the slot has a width, and wherein the focusing element has a diameter that is equal to or less than 250 μ

m.

14. The optical backplane of claim 12 further comprising an alignment mark to facilitate the alignment of the receptacle, the alignment mark being disposed on the substrate, the material layer, a layer above the material layer, or a layer between the substrate and the material layer, and wherein the alignment mark is at a predetermined distance from the first end of the core body.

15. The optical backplane claim 1 further comprising an angle-reflecting structure disposed at the first end of the core body.

16. A method of forming an integrated optical backplane, the method comprising the steps of:

(a) forming at least a first waveguide layer, the first waveguide layer having at least a first cladding layer and at least a first core body, the first core body having a first end, a second end, and at least a portion in contact with the first cladding layer;

(b) forming a material layer above the first waveguide layer, the material layer having a top surface and a bottom surface, with the bottom surface facing the first waveguide layer; and

(c) forming a focusing element at the top surface of the material layer, the focusing element being located above the first end of the first core body.

17. The method of claim 16 wherein the material layer comprises a photorefractive material, and wherein step (c) comprises exposing the material layer to a pattern of actinic radiation such that a spatial variation in the refractive index occurs in the material layer at a location disposed above the first end of the first core body.

18. The method of claim 17 wherein the spatial variation comprises the form of a plano-convex lens.

19. The method of claim 17 wherein the spatial variation comprises the form a grating.

20. The method of claim 19 wherein the spatial variation comprises a plurality of concentric rings.

21. The method of claim 17 wherein the step of exposing the material layer to a pattern of actinic radiation comprises the step of passing the actinic radiation through a grayscale mask.

22. The method of claim 16 wherein step (c) comprises removing portions of the material layer to define a bump having a convex form.

23. The method of claim 22 wherein the material layer has a first refractive index, and wherein step (c) further comprises the step of forming a cover layer over the bump and at least a portion of the material layer, the cover layer having a second refractive index that is less than the first refractive index.

24. The method of claim 16 wherein the material layer has a first refractive index, and wherein step (c) comprises:

forming a recess in the material layer at its top surface, the recess being located above the first end of the first core body; and

filling the recess with material having a second refractive index different from the first refractive index.

25. The method of claim 24 wherein the second refractive index is greater than the first refractive index.

26. The method of claim 16 wherein step (c) comprises removing portions of the material layer to define a grating.

27. The method of claim 16 wherein step (c) comprises removing portions of the material layer to define a plurality of concentric rings.

28. The method of claim 16 further comprising the steps of:

forming an alignment mark on the top surface of the material layer; and

mounting a receptacle on the top surface of the material layer, the receptacle constructed to receive a connector having an optical fiber, the mounting step including the step of aligning a feature of the receptacle to the alignment mark.

29. The method of claim 16 further comprising the steps of:

forming an alignment mark on the substrate or a layer below the material layer, the alignment mark being formed prior to the formation of the material layer; and

mounting a receptacle on the top surface of the material layer, the receptacle constructed to receive a connector having an optical fiber, the mounting step including the step of aligning a feature of the receptacle to the alignment mark.