Manufacturing a microlens at the extremity of a lead waveguide

• US 7,474,821 B2
• Filed: 08/25/2005
• Issued: 01/06/2009
• Est. Priority Date: 08/25/2004
• Status: Expired due to Fees

• Current Assignee: Lumentum DOO Opticna Vlakna
• Original Assignee: Lumentum doo
• Inventors: Pinet, Éric, Donlagic, Denis, Cibula, Edvard
• Primary Examiner(s): WONG, TINA MEI SENG
• Application Number:
  US11/660,994
• Publication Number:
  US 20080019639A1
• Time in Patent Office: 1,230 Days
• Field of Search: None
• US Class Current: 385/33
• CPC Class Codes: B29D 11/00692 combined with lenses
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements

Abstract

Variants of a method for manufacturing a microlens of any desired shape at the extremity of a lead waveguide are provided. A lens element having a non-uniform radial etchability profile is provided at the extremity of the lead waveguide. Preferably, the etchability profile is determined by a non-uniform radial distribution of dopants in the lens element. A spacer may optionally be placed between the waveguide and the lens element. The lens element is then brought down to an appropriate length and etched to its final shape which is mainly determined by the dopant distribution. An optical coupling assembly having a non-uniform radial distribution of dopants therein is also provided.

Claims

1. A method for manufacturing a microlens having a desired shape at an extremity of a lead waveguide, the method comprising the steps of:

a) positioning a first end of an elongated optical structure in end to end alignment with the extremity of the lead waveguide, said optical structure having a second end opposite said first end, said second end having a radially non-uniform etchability profile selected to define said desired shape;

b) permanently joining the first end of the optical structure to said extremity of the waveguide; and

c) processing the second end of the optical structure to obtain said microlens, said processing comprising the substeps of;

i. adjusting a length of said optical structure; and

ii. etching said second end of the optical structure to obtain said desired shape.

2. The method according to claim 1, wherein said optical structure comprises a spacer portion at said first end and a lens portion at said second end.

3. The method according to claim 2, wherein said spacer and lens portions form a monolithic block.

4. The method according to claim 2, comprising an additional step before step a) of manufacturing said optical structure, said additional step comprising the substeps of:

i. positioning a spacer element in end to end alignment with a lens element, said lens element being provided with said etchability profile;

ii. permanently joining said lens element to said spacer element; and

iii. adjusting a length of said spacer element.

5. The method according to claim 4, wherein said lens element comprises a spacer sub-portion at said first end and a lens sub-portion at said second end, said spacer and lens sub-portions forming a monolithic block.

6. The method according to claim 1, wherein the microlens obtained by the processing of step c) is contiguous to the extremity of the lead waveguide.

7. The method according to claim 4, wherein said spacer element is made of a material selected from the group consisting of pure silica glass and composite glass.

8. The method according to claim 1 wherein at least the second end of the optical structure is made of composite glass having at least one type of dopants therein, said dopants having a radial distribution profile defining said non-uniform etchability profile.

9. The method according to claim 8, wherein said radial distribution profile of dopants has a maximum at a center of said second end of the optical structure and decreases towards sides thereof.

10. The method according to claim 8, wherein said radial distribution profile of dopants has a minimum at a center of said second end of the optical structure and increases towards sides thereof.

11. The method according to claim 8, wherein at least one of the at least one type of dopants increases a refractive index in said second end of the optical structure.

12. The method according to claim 8, wherein at least one of the at least one type of dopants decreases a refractive index in said second end of the optical structure.

13. The method according to claim 8, wherein at least two of said at least one type of dopants and the radial distribution thereof are selected to provide a predetermined refractive index profile across said second end of the optical structure.

14. The method according to claim 8, wherein at least two of said at least one type of dopants and the radial distribution thereof are selected to provide a uniform refractive index throughout said second end of the optical structure.

15. The method according to claim 1, wherein said lead waveguide is an optical fiber.

16. The method according to claim 1, wherein the permanent joining of step b) comprises fusion splicing said first end of the optical structure to said extremity of the lead waveguide.

17. The method according to claim 4, wherein the permanent joining of substep a) ii comprises fusion splicing said lens element to said spacer element.

18. The method according to claim 1, wherein the adjusting of substep c) i. comprises using at least one of the techniques selected from the group consisting of cleaving and polishing said second end of the optical structure.

19. The method according to claim 4, wherein the adjusting of substep a) iii. comprises using at least one of the techniques selected from the group consisting of cleaving and polishing said spacer element.

20. The method according to claim 1, wherein step c) comprises and additional substep iii. of finishing a surface of said microlens.

21. The method according to claim 1, wherein step c) ii. further comprises propagating a light beam through said lead waveguide towards said optical structure, monitoring light outputted from said optical structure and controlling said etching based on said monitoring.

22. The method according to claim 1, wherein step c) ii. further comprises also etching an outer surface of the spacer portion to reduce a diameter thereof to a size smaller than a diameter of the lead waveguide.

23. The method according to claim 1, wherein said etchability profile of the second end of the optical structure is designed so that said desired shape of the microlens is selected from the group comprising of spherical, elliptic, conical, trapezoidal, parabolic, and hyperbolic profiles and truncations thereof.

24. A method for manufacturing a microlens having a desired shape at an extremity of a lead waveguide, the method comprising the steps of:

a) positioning a first end of an elongated spacer element in end to end alignment with the extremity of the lead waveguide;

b) permanently joining the first end of the spacer element to said extremity of the waveguide;

c) processing a second end of the spacer element opposite the first end to adjust a length thereof;

d) positioning a first end of an elongated lens element in end to end alignment with the second end of the spacer element, said lens element having a second end opposite the first end, said second end having a radially non-uniform etchability profile selected to define said desired shape;

e) permanently joining the first end of the lens element to said second end of the spacer element; and

f) processing the second end of the lens element to obtain said microlens, said processing comprising the substeps of;

i. adjusting a length of said lens element; and

ii. etching said second end of the lens element to obtain said desired shape.

25. The method according to claim 24, wherein said lens element comprises a spacer sub-portion at said first end and a lens sub-portion at said second end, said spacer and lens portions forming a monolithic block.

26. The method according to claim 25, wherein the lens element is made of composite glass having at least one type of dopants therein, said dopants having a radial distribution profile defining said non-uniform etchability profile.

27. The method according to claim 24, wherein said spacer element is made of a material selected from the group consisting of pure silica glass and composite glass.

28. The method according to claim 24, wherein the lens element is made of composite glass having at least one type of dopants therein, said dopants having a radial distribution profile defining said non-uniform etchability profile.

29. The method according to claim 28, wherein said radial distribution profile of dopants has a maximum at a center of said lens element and decreases towards sides thereof.

30. The method according to claim 28, wherein said radial distribution profile of dopants has a minimum at a center of said lens element and increases towards sides thereof.

31. The method according to claim 28, wherein at least one of the at least one type of dopants increases a refractive index in said lens element.

32. The method according to claim 28, wherein at least one of the at least one type of dopants decreases a refractive index in said lens element.

33. The method according to claim 28, wherein at least two of said at least one type of dopants and the radial distribution thereof are selected to provide a predetermined refractive index profile across said lens element.

34. The method according to claim 28, wherein at least two of said at least one type of dopants and the radial distribution thereof are selected to provide a uniform refractive index throughout said lens element.

35. The method according to claim 24, wherein said lead waveguide and said lens element are optical fibers.

36. The method according to claim 24, wherein said spacer element is a glass rod.

37. The method according to claim 24, wherein the permanent joining of step b) comprises fusion splicing said first end of the spacer element to said extremity of the waveguide.

38. The method according to claim 24, wherein the permanent joining of step e) comprises fusion splicing said first end of the lens element to said second end of the spacer element.

39. The method according to claim 24, wherein the processing of step c) comprises using at least one of the techniques selected from the group consisting of cleaving and polishing said second end of the spacer element.

40. The method according to claim 24, wherein the adjusting of substep f) i. comprises using at least one of the techniques selected from the group consisting of cleaving and polishing said second end of the lens element.

41. The method according to claim 24, wherein step f) comprises and additional substep iii. of finishing a surface of said microlens.

42. The method according to claim 24, wherein step f) ii. further comprises propagating a light beam through said lead waveguide towards said optical structure, monitoring light outputted from said optical structure and controlling said etching based on said monitoring.

43. The method according to claim 24, wherein step f) ii. further comprises also etching an outer surface of the spacer element to reduce a width thereof to a size smaller than a width of the lead waveguide.

44. The method according to claim 24, wherein said etchability profile of the second end of the lens element is designed so that said desired shape of the microlens is selected from the group comprising or spherical, elliptic, conical, trapezoidal, parabolic, and hyperbolic profiles and truncations thereof.

45. A light coupling assembly, comprising:

a lead waveguide having a coupling extremity;

an optical structure having opposite first and second ends, the first end being permanently joined to the coupling extremity of the waveguide, and the second end being shaped as a microlens of a generally continuous profile, said second end having a radial distribution of dopants therein following a generally continuous gradient profile.

46. The light coupling assembly according to claim 45, wherein said dopants generate a generally continuous refractive index radial gradient in said second end of the optical structure.

47. The light coupling assembly of claim 45, wherein said optical structure comprises a spacer portion at said first end and a lens portion at said second end.

48. The light coupling assembly according to claim 47, wherein said spacer and lens portions form a monolithic block.

49. The light coupling assembly according to claim 47, wherein said spacer portion is defined by a spacer element permanently joined to a lens element, said lens element defining said lens portion.

50. The light coupling assembly according to claim 49, wherein said spacer element is a glass rod.

51. The light coupling assembly according to claim 49, wherein said spacer is element is made of a material selected from the group consisting of pure silica glass and composite glass.

52. The light coupling assembly according to claim 49, wherein said spacer element has non-homogenous optical properties along at least one of a longitudinal direction and a radial direction.

53. The light coupling assembly according to claim 45, wherein said dopants are selected to increase a refractive index of the second end of the optical structure.

54. The light coupling assembly according to claim 45, wherein said dopants are selected to decrease a refractive index of the second end of the optical structure.

55. The light coupling assembly according to claim 45, wherein said dopants are of at least two different types, said types and the radial distribution of said dopants being selected to provide a predetermined refractive index profile in said microlens.

56. The light coupling assembly according to claim 45, wherein said profile of the microlens is symmetrical with respect to a longitudinal axis of said assembly.

57. The light coupling assembly according to claim 45, wherein said profile of the microlens is asymmetrical with respect to a longitudinal axis of said assembly.

58. The light coupling assembly according to claim 45, wherein said profile of the microlens is selected from the group comprising or spherical, elliptic, conical, trapezoidal, parabolic, and hyperbolic profiles and truncations thereof.

59. The light coupling assembly according to claim 45, wherein said microlens is plano-convex.

60. The light coupling assembly according to claim 45, wherein said microlens is plano-concave.

61. The light coupling assembly according to claim 45, wherein said optical structure has a diameter larger than a diameter of the lead waveguide.

62. The light coupling assembly according to claim 45, wherein said optical structure has a diameter substantially equal to a diameter of the lead waveguide.

63. The light coupling assembly according to claim 45, wherein said optical structure has a diameter smaller than a diameter of the lead waveguide.

64. The light coupling assembly according to claim 45, wherein said optical structure has a diameter larger than a diameter of a core of the lead waveguide.