Single mode propagation in fibers and rods with large leakage channels

• US 20060263024A1
• Filed: 05/20/2005
• Published: 11/23/2006
• Est. Priority Date: 05/20/2005
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Wong, William, Fermann, Martin E., Dong, Liang
• Granted Patent: US 7,787,729 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/02 Optical fibres with cladding with or without a coating
• CPC Class Codes: G02B 6/02009 Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres
• CPC Class Codes: G02B 6/02033 Core or cladding made from organic material, e.g. polymeric material G02B1/04 takes precedence
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
• CPC Class Codes: G02B 6/02361 Longitudinal structures forming multiple layers around the core, e.g. arranged in multiple rings with each ring having longitudinal elements at substantially the same radial distance from the core, having rotational symmetry about the fibre axis
• CPC Class Codes: G02B 6/02366 Single ring of structures, e.g. "air clad"
• CPC Class Codes: G02B 6/02371 Cross section of longitudinal structures is non-circular
• CPC Class Codes: G02B 6/024 with polarisation maintaining properties
• CPC Class Codes: G02B 6/036 core or cladding comprising multiple layers multicore optical fibres G02B6/02042; microstructured properties G02B6/02295; omniguide fibres G02B6/023
• CPC Class Codes: G02B 6/03633 arranged - -
• CPC Class Codes: G02B 6/03694 Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties
• CPC Class Codes: G02B 6/24 Coupling light guides
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• 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
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02F 1/0134 in optical waveguides
• CPC Class Codes: H01S 2302/00 Amplification / lasing wavelength
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/02 Constructional details housings or packages of fibre lasers H01S3/06704
• CPC Class Codes: H01S 3/06708 : Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering optical fibres as passive waveguides G02B6/02
• CPC Class Codes: H01S 3/06729 : Peculiar transverse fibre profile
• CPC Class Codes: H01S 3/06745 : Tapering of the fibre, core or active region
• CPC Class Codes: H01S 3/06754 : Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094007 : Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/1618 : ytterbium
• CPC Class Codes: H01S 3/2308 : Amplifier arrangements, e.g. MOPA
• CPC Class Codes: H01S 3/302 : in an optical fibre

Abstract

Various embodiments include large cores fibers that can propagate few modes or a single mode while introducing loss to higher order modes. Some of these fibers are holey fibers that comprising cladding features such as air-holes. Additional embodiments described herein include holey rods. The rods and fibers may be used in many optical systems including optical amplification systems, lasers, short pulse generators, Q-switched lasers, etc. and may be used for example for micromachining.

Claims

1. An optical fiber for propagating at least one lower order mode having a wavelength, λ

, while limiting propagation of higher order modes having a wavelength, λ

, by providing said higher order modes with a higher loss than said at least one lower order mode at said wavelength, λ

, said optical fiber comprising;

a first cladding region comprising one or more cladding features; and

a core region surrounded by the said first cladding region, said cladding features configured to substantially confine propagation of said lower order modes to said core region, said core region having a width of at least about 20 micrometers,

wherein said core region is configured to provide a loss for said higher order modes of at least about 0.5 dB.

2. The optical fiber of claim 1, wherein said core region is configured to provide a loss for said higher order modes of at least about 1 dB.

3. The optical fiber of claim 1, wherein said width of said core region is at least about 40 micrometers.

4. The optical fiber of claim 1, wherein said features have a minimum size, d, yielding a ratio of d/λ

that is at least about 10.

5. The optical fiber of claim 4, wherein said ratio of d/λ

is at least about 20.

6. The optical fiber of claim 1, wherein said cladding features are arranged in a single row.

7. The optical fiber of claim 1, wherein said core and cladding regions are in a substantially optically transmissive main body of said optical fiber, said main body comprising material substantially optically transmissive of said wavelength, λ

, said main body having a width and thickness at least about 250 μ

m so as to reduce mode coupling of said lower order modes to said higher order modes.

8. The optical fiber of claim 7, wherein said width and thickness of said main body is at least about 500 μ

m.

10. An optical amplifier comprising an optical fibers according to claim 1, wherein said core region is doped to provide optical gain.

11. A system comprising the optical amplifier of claim 10, wherein output pulse energy is in excess of 1 μ

J.

12. An optical system for generation of high power solitons comprising the optical fiber of claim 1.

13. A laser system comprising the optical fiber of claim 1, wherein said optical fiber is doped with dopants that provide said optical fiber with gain and said optical fiber is optically coupled to reflective elements that form an optical resonator.

15. A fiber laser according to claim 13, wherein said fiber comprises a Nd doped fiber configured to lase between about 900 to 960 nanometers.

16. A fiber laser according to claim 13, wherein said fiber comprises a ytterbium doped fiber configured to lase between about 900 to 1000 nanometers.

17. A chirped pulse amplification system for the amplification of picosecond or femtosecond pulses comprising the fiber of claim 10 and a pulse compressor.

19. A laser micro-machining system comprising the chirped pulse amplification system of claim 17 and a positioning system.

24. An optical fiber according to claim 1, wherein the core and cladding regions comprise polymer materials.

9. (canceled)

14. (canceled)

18. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. An optical fiber for propagating at least one lower order mode having a wavelength, λ

, while limiting propagation of higher order modes having a wavelength, λ

, by providing said higher order modes with a higher loss than said at least one lower order mode at said wavelength, λ

, said optical fiber comprising;

a first cladding region comprising one or more cladding features configured to form a partially enclosed region, said partially enclosed region having at least one opening therein formed by one or more spaces in said partially enclosed region, said one or more features having a maximum feature size, d, and a maximum bridge width, a, said maximum bridge width in part determining the size of said one or more spaces in said partially enclosed region; and

a core region surrounded by the said first cladding region, said cladding features configured to substantially confine propagation of said lower order modes to said core region,

wherein said maximum bridge width, a, and said maximum feature size, d, have respective values that yield a ratio of a/λ

that is at least about 5 and a ratio of d/λ

that is at least about 10 thereby providing an increased effective core size, confinement of said at least one lower order mode, and reduction of said higher order modes.

29. The optical fiber of claim 28, wherein said cladding features comprise regions of a material with a lower refractive index than said core region.

30. The optical fiber of claim 28, wherein said ratio of d/λ

is at least about 20.

31. The optical fiber of claim 28, wherein said ratio of d/λ

is at least about 40.

32. The optical fiber of claim 28, wherein said ratio of a/λ

is at least about 10.

33. The optical fiber of claim 28, said cladding features are substantially arranged in a circle.

34. The optical fiber of claim 28, said cladding features are substantially arranged no more than two rings around said core region.

35. The optical fiber of claim 34, said cladding features are substantially arranged no more than one ring around said core region.

36. The optical fiber of claim 28, wherein said cladding features have two dimensional asymmetries that provide birefringence.

37. The optical fiber of claim 28, further comprising stress elements that produce two dimensional asymmetries and provide birefringence.

38. The optical fiber of claim 28, further comprising at least one stress producing region.

39. The optical fiber of claim 28, wherein said core region is between about 20 um and 300 um in diameter.

40. The optical fiber of claim 28, wherein said core region is doped with at least one rare earth ion that provides gain.

41. The optical fiber of claim 40, wherein said core region is doped with ytterbium ions.

42. The optical fiber of claim 40, wherein said core region is doped with erbium ions.

43. The optical fiber of claim 28, wherein said first cladding region is surrounded by a second cladding region.

44. The optical fiber of claim 43, wherein said second cladding region comprises a polymer with a refractive index lower than said core region.

45. The optical fiber of claim 43, wherein said second cladding region comprises at least one cladding feature and a bridge.

46. The optical fiber of claim 43, wherein said fiber is spliced to a length of a second non-waveguiding fiber.

47. The optical fiber of claim 43, wherein said fiber is spliced to a length of a second fiber with a single cladding essentially matched in dimension to the second cladding of the said fiber and pump power is coupled into the second fiber.

48. The optical fiber of claim 28, further comprising a tapered end.

49. The optical fiber of claim 48, wherein said tapered end is spliced and mode matched to a single or few mode fiber.

50. The optical fiber of claim 28, wherein cladding features comprise air holes and said air-holes are collapsed at each end, thereby sealing said air holes and producing substantially air-hole free ends.

51. The optical fiber of claim 28, wherein the optical waveguide is constructed from a ceramic, crystalline, glass, or plastic material.

52. The optical fiber of claim 40, further comprising a non-waveguide fiber optically coupled to at least one of ends of said optical fiber.

53. (canceled)

54. (canceled)

55. (canceled)

56. (canceled)

57. (canceled)

58. An optical rod for propagating at least one lower order mode having a wavelength, λ

, while limiting propagation of higher order modes having a wavelength, λ

, by providing said higher order modes with a higher loss than said at least one lower order mode at said wavelength, λ

, said optical rod comprising;

a first cladding region comprising one or more cladding features; and

a core region surrounded by the said first cladding region, said cladding features configured to substantially confine propagation of said lower order modes to said core region, said core region having a width of at least about 20 micrometers,

wherein said core region is configured to provide a loss for said higher order modes of at least about 0.5 dB.

59. The rod of claim 58, wherein said core region is configured to provide a loss for said higher order modes of at least about 1 dB.

60. The rod of claim 58, wherein said width of said core region is at least about 40 micrometers across.

61. The rod of claim 58, wherein said features have a minimum feature size, d, yielding a ratio of d/λ

that is at least about 10.

62. The rod of claim 58, wherein said core and cladding regions are in a substantially optically transmissive main body of said rod, said main body comprising material substantially optically transmissive of said wavelength, λ

, said main body having a width and thickness at least about 250 μ

m so as to reduce mode coupling of said at least one lower order mode to said higher order modes.

63. (canceled)

64. (canceled)

65. (canceled)

66. (canceled)

67. A holey waveguide rod, comprising:

a ceramic or crystalline laser material;

at least one core region in said ceramic or crystalline laser material, said core region being bounded by features surrounding said core region; and

at least one cladding region in said ceramic or crystalline laser material, said features disposed within the physical extent of said cladding region.

68. The holey waveguide rod of claim 67, wherein said features comprises air-holes.

69. A holey waveguide rod amplifier according to claim 67, wherein said ceramic or crystalline waveguide rod comprises Ti:

sapphire, Yb;

Y₂O₃, Nd;

YAG, Nd;

YLF, Nd;

YVO₄, Nd;

KGW, Yb;

KGW or Yb;

KYW.

70. A method of manufacturing a holey waveguide rod amplifier, comprising:

providing a ceramic or crystalline laser material;

forming at least one air hole configured to form a core region in said ceramic or crystalline laser material, said core region being bounded by said at least one air hole, said at least one air hole comprising a cladding region in said ceramic or crystalline laser material.

71. (canceled)

72. (canceled)

73. (canceled)

74. (canceled)

75. An optical fiber for propagating at least one lower order modes having a wavelength, λ

, while limiting propagation of higher order modes having a wavelength, λ

, by providing said higher order modes with a higher loss than said at least one lower order mode at said wavelength, λ

, said optical fiber comprising;

a cladding; and

a core, said core region having a width of at least about 20 micrometers, wherein said fiber is configured such that (i) the at least one lower order mode has no more than 1.0 db of loss at a bending radius of at 30 centimeters and (ii) said higher order modes have a loss of at least 0.5 dB.

76. The optical fiber of claim 75, wherein the number of lower order modes is no more than 10.

77. The optical fiber of claim 76, wherein the number of lower order modes is no more than 5.

78. The optical fiber of claim 77, wherein the number of lower order modes is no more than 1.

79. The optical fiber of claim 78, wherein the fundamental mode has no more than 0.5 dB of loss at a bending radius of 10 centimeters.