Evanescent optical coupling between a waveguide formed on a substrate and a side-polished fiber

• US 6,625,349 B2
• Filed: 06/12/2001
• Issued: 09/23/2003
• Est. Priority Date: 06/27/2000
• Status: Expired due to Fees

• Current Assignee: Intelligent Fiber Optic Systems Corporation
• Original Assignee: Oluma, Inc. (Intelligent Fiber Optic Systems, Inc.)
• Inventors: Pi, Bo, Zhao, Shulai
• Primary Examiner(s): Ullah, Akm Enayet
• Assistant Examiner(s): Doan, Jennifer
• Application Number:
  US09/880,722
• Publication Number:
  US 20020076150A1
• Time in Patent Office: 833 Days
• Field of Search: 385/15, 385/16, 385/18, 385/30, 385/31, 385/32, 385/37, 385/39, 385/50
• US Class Current: 385/30
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/2804 forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
• CPC Class Codes: G02B 6/2826 using mechanical machining means for shaping of the couplers, e.g. grinding or polishing grinding, polishing in general B24
• CPC Class Codes: G02B 6/2852 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
• CPC Class Codes: G02B 6/29332 Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency non wavelength-selective light guide couplers G02B6/28
• CPC Class Codes: G02B 6/29334 Grating-assisted evanescent light guide couplers, i.e. comprising grating at or functionally associated with the coupling region between the light guides, e.g. with a grating positioned where light fields overlap in the coupler
• CPC Class Codes: G02B 6/29355 Cascade arrangement of interferometers
• CPC Class Codes: G02B 6/30 for use between fibre and thin-film device
• CPC Class Codes: G02B 6/3502 involving direct waveguide displacement, e.g. cantilever type waveguide displacement involving waveguide bending, or displacing an interposed waveguide between stationary waveguides
• CPC Class Codes: G02B 6/3536 involving evanescent coupling variation, e.g. by a moving element such as a membrane which changes the effective refractive index mode converters G02B6/14; adjustable lateral coupling between waveguides G02B6/283; electro- optical refractive index variations G02F1/0118
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/3636 the mechanical coupling means being grooves G02B6/3652 takes precedence
• CPC Class Codes: G02B 6/3644 the coupling means being through-holes or wall apertures

Abstract

Techniques for coupling optical energy between a side-polished port of a fiber in one substrate and a coupling port of a waveguide in another substrate.

Claims

1. A device, comprising:

a fiber module having a first substrate with a first surface fabricated to form an elongated groove with two through holes penetrating said first substrate and formed on both ends of said groove, and a fiber engaged to said first substrate by passing through both said through holes to have a portion laid in said elongated groove, wherein cladding of said portion is removed to form a fiber coupling port for evanescently coupling energy into and out of said fiber; and

a waveguide module having a second substrate configured to have an optical waveguide with a waveguide portion to form a waveguide coupling port for evanescently coupling energy into and out of said waveguide,

wherein said waveguide module is engaged to said fiber module to place said elongated groove substantially parallel to said waveguide and to interface said fiber coupling port with said waveguide coupling port for evanescent optical coupling between said waveguide and said fiber.

2. The device as in claim 1, wherein said second substrate has a second surface parallel to and facing said first surface of said first substrate, and wherein said waveguide is formed in said substrate and said waveguide portion is at the same plane of said second surface.

3. The device as in claim 1, wherein said second substrate has a second surface parallel to and facing said first surface of said first substrate and said waveguide is formed over said second surface on said substrate, and wherein said waveguide module further includes a first cladding layer formed between said second surface and said waveguide and a second cladding layer formed to cover said waveguide, and a portion of said second cladding layer is removed to form said waveguide coupling port.

4. The device as in claim 3, wherein said waveguide is a ridge waveguide.

5. The device as in claim 3, wherein said waveguide is a slab waveguide.

6. The device as in claim 3, wherein said waveguide is a channel waveguide.

7. The device as in claim 1, wherein said waveguide is further configured to include an optical grating formed in said waveguide portion to assist said evanescent optical coupling between said waveguide and said fiber.

8. The device as in claim 7, further comprising an optical grating formed in cladding of said fiber to assist said evanescent optical coupling between said waveguide and said fiber.

9. The device as in claim 7, further comprising an optical grating formed in a core of said fiber to assist said evanescent optical coupling between said waveguide and said fiber.

10. The device as in claim 1, further comprising an optical grating formed between said waveguide and said fiber to assist said evanescent optical coupling between said waveguide and said fiber.

11. The device as in claim 1, wherein said waveguide module further includes a second waveguide formed on said second substrate and engaged to said waveguide to receive at least a portion of an optical signal in said fiber through optical coupling with said waveguide.

12. The device as in claim 1, further comprising at least one buffer layer in said elongated groove between said first substrate and said fiber to reduce a mechanical or thermal stress.

13. A method, comprising:

engaging a fiber to a first substrate by passing through two through holes formed in said first substrate to lay a portion of said fiber in an elongated groove formed between said through holes;

removing a portion of cladding of said portion to form a fiber coupling port to allow for evanescent optical coupling into and out of said fiber;

forming a waveguide coupling port in a waveguide formed on a second substrate to allow for evanescent optical coupling into and out of said waveguide; and

positioning said first and said second substrates relative to each other to place said fiber coupling port in contact with or near said waveguide coupling port to allow for evanescent optical coupling between a guided optical mode in said fiber and a guided optical mode in said waveguide.

14. The method as in claim 13, further comprising providing a diffraction grating to assist optical coupling between said fiber and said waveguide.

15. The method as in claim 13, further comprising forming at least one buffer layer in said elongated groove between said substrate and said fiber to reduce a mechanical or thermal stress between said fiber and said substrate.

16. The method as in claim 13, further comprising forming another waveguide in said second substrate which is optically coupled to said waveguide to exchange optical energy between said fiber and said another waveguide through said waveguide.

17. A device, comprising:

a waveguide substrate;

an optical waveguide formed in said waveguide substrate and configured to have input and output waveguide coupling ports at two different positions for evanescently coupling energy into and out of said waveguide;

an input fiber-waveguide coupler engaged to an input fiber to receive input light from said input fiber and engaged to said waveguide to couple said input light into said waveguide;

an output fiber-waveguide coupler engaged to an output fiber and coupled a position in said waveguide to receive said input light in said waveguide to produce output light in said output fiber,

wherein each fiber-waveguide coupler includes a substrate to form an elongated groove in which a portion of said input or output fiber is engaged, and wherein cladding of said portion is removed to form a fiber coupling port for evanescent optical coupling;

a first optical grating disposed and configured to assist coupling between said fiber and said input waveguide coupling port; and

a second optical grating disposed and configured to assist coupling between said fiber and said output waveguide coupling port, wherein said waveguide between said input and output fiber-waveguide couplers includes a semiconductor gain section configured to amplify said input light.

18. The device as in claim 17, wherein said semiconductor gain section includes a multiple quantum well structure.

19. The device as in claim 17, wherein said first optical grating is formed in said waveguide.

20. The device as in claim 17, wherein said first optical grating is formed in said fiber.

21. The device as in claim 17, further comprising an overlay layer between said input waveguide coupling port and said fiber in which said first optical grating is formed.

22. The device as in claim 17, further comprising a light absorber at an end of said waveguide to absorb light in said waveguide that passes through said output fiber-waveguide coupler.

23. The device as in claims 17, wherein each fiber-waveguide coupler includes a substrate to form an elongated groove with one through hole penetrating said substrate and formed on one end, and said input or output fiber is engaged to said substrate by passing through said one through hole to have a portion laid in said elongated groove.

24. A device, comprising:

a waveguide substrate;

an optical waveguide formed in said waveguide substrate and configured to have input and output waveguide coupling ports at two different positions for evanescently coupling energy into and out of said waveguide;

an input fiber-waveguide coupler engaged to an input fiber to receive input light from said input fiber and engaged to said waveguide to couple said input light into said waveguide;

an output fiber-waveguide coupler engaged to an output fiber and coupled a position in said waveguide to receive said input light in said waveguide to produce output light in said output fiber,

wherein each fiber-waveguide coupler includes a substrate to form an elongated groove in which a portion of said input or output fiber is engaged, and wherein cladding of said portion is removed to form a fiber coupling port for evanescent optical coupling;

a first optical grating disposed and configured to assist coupling between said fiber and said input waveguide coupling port; and

a second optical grating disposed and configured to assist coupling between said fiber and said output waveguide coupling port, wherein each fiber-waveguide coupler includes a substrate to form an elongated groove with two through holes penetrating said substrate and formed on both ends, and said input or output fiber is engaged to said substrate by passing through both said through holes to have a portion laid in said elongated groove.

25. A device, comprising:

a first waveguide substrate fabricated to support a first optical waveguide which is configured to have a first waveguide coupling port to allow evanescent coupling into and out of said first waveguide along a direction transverse to said first waveguide;

a second waveguide substrate fabricated to support a second optical waveguide which is configured to have a second waveguide coupling port to allow evanescent coupling into and out of said second waveguide along a direction transverse to said second waveguide; and

a fiber-waveguide coupler having a base substrate with a first surface and a second opposing surface and a fiber engaged to said base substrate to have a first fiber portion over said first surface and a second fiber portion on said second surface, each of said first and said second fiber portions has a fiber coupling port to allow for evanescently coupling optical energy into or out of said fiber

wherein said fiber-waveguide coupler is positioned between said first and said second waveguide substrates so that said first waveguide coupling port and said first fiber portion face each other to allow for evanescent coupling therebetween, and said second waveguide coupling port and said second fiber portion face each other to allow for evanescent coupling there between.

26. The device as in claim 25, further comprising:

a first grating formed between said first waveguide coupling port and said first fiber portion to assist optical coupling; and

a second grating formed between said second waveguide coupling port and said second fiber portion to assist optical coupling.

27. The device as in claim 25, wherein said first waveguide substrate further comprises an additional waveguide that is optically coupled to said first optical waveguide.

28. A device, comprising:

a first module having a first substrate and an optical fiber, said first substrate comprising (1) first and second opposing substrate surfaces, and (2) an elongated groove formed over said first substrate surface, wherein said optical fiber has a first fiber portion engaged in said elongated groove, and fiber cladding of said first fiber portion is removed to form a fiber coupling port for evanescently coupling energy into or out of said optical fiber;

a second module positioned adjacent to said first module, said second module having a second substrate which is configured to support a planar waveguide, said planar waveguide having a coupling port interfaced with said fiber coupling port for evanescent coupling between said optical fiber and said planar waveguide; and

an optical grating positioned to assist optical coupling between said optical fiber and said planar waveguide, wherein said first substrate includes a first opening located at a first end of said elongated groove and formed through said first substrate to extend between said first and second substrate surfaces, and wherein said optical fiber passes through said first opening to have a second fiber portion positioned over said second substrate surface.

29. The device as in claim 28, wherein said optical grating is formed in said planar waveguide.

30. The device as in claim 28, wherein said optical grating is formed in said fiber.

31. The device as in claim 28, wherein said optical grating is formed between said fiber and said planar waveguide.

32. The device as in claim 28, wherein said first substrate further includes a second opening located at a second end of said elongated groove and formed through said first substrate to extend between said first and second substrate surfaces, and wherein said optical fiber further passes through said second opening to have a third fiber portion positioned over said second substrate surface.

33. The device as in claim 28, further comprising at least one buffer layer in said first elongated groove between said first substrate and said fiber to reduce a mechanical or thermal stress.

34. The device as in claim 28, further comprising an optical switch having first and second input ports and first and second output ports, said first input port coupled to a first end of said optical fiber and said first output port coupled to a second end of said optical fiber, wherein said optical switch is operable to connect said first input port to said first output port in one operating state and to connect said first input port to said second output port and said second input port to said first output port in a second operating state.

35. A device, comprising:

a first module having a first substrate and an optical fiber, said first substrate comprising first and second opposing substrate surfaces, and (2) first and second elongated groove formed over said first substrate surface, wherein said optical fiber has a first fiber portion engaged in said first elongated groove and a second fiber portion engaged in said second elongated groove, wherein fiber claddings of said first and said second fiber portions are removed to form first and second fiber coupling ports, respectively for evanescently coupling energy into or out of said optical fiber;

a second module positioned adjacent to said first module, said second module having a second substrate which is configured to support a planar waveguide, said planar waveguide having a first waveguide coupling port interfaced with said first fiber coupling port and a second waveguide coupling port interfaced with said second fiber coupling port, both for evanescent coupling between said optical fiber and said planar waveguide, wherein said first substrate has a third elongated groove on said second substrate surface to engage a third fiber portion and said adjustable element is formed over or in said third fiber portion; and

an adjustable element formed in either said fiber between said first and second fiber coupling ports or said planar waveguide between said first and said second waveguide coupling ports, and configured to produce a change in light guided in said fiber or said planar waveguide in response to an external control signal.

36. The device as in claim 35, further comprising:

a first optical grating positioned to assist optical coupling between said first waveguide coupling port and said first fiber coupling port; and

a second optical grating positioned to assist optical coupling between said second waveguide coupling port and said second fiber coupling port.

37. The device as in claim 35, wherein said adjustable element includes an adjustable optical grating.

38. The device as in claim 35, wherein said adjustable element includes a material whose refractive index changes in response to said external control signal.

39. The device as in claim 35, wherein an opening is formed at one end of each elongated groove and penetrates through said first substrate, and wherein said fiber passes through said opening to have a fiber portion positioned over said second substrate surface.