Single mode propagation in fibers and rods with large leakage channels

• US 7,787,729 B2
• Filed: 05/20/2005
• Issued: 08/31/2010
• Est. Priority Date: 05/20/2005
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Wong, William, Fermann, Martin E., Dong, Liang
• Primary Examiner(s): Peng; Charlie
• Assistant Examiner(s): El Shammaa; Mary A
• Application Number:
  US11/134,856
• Publication Number:
  US 20060263024A1
• Time in Patent Office: 1,929 Days
• Field of Search: 385/123
• US Class Current: 385/123
• 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 lower order modes, having order N or less and having a wavelength, λ

,while limiting propagation of all higher order modes with order greater than N by providing said all higher order modes with a higher loss than said lower order modes at said wavelength, λ

, said optical fiber comprising;

a first cladding region comprising a plurality of lower-index cladding features, each of said plurality of lower-index cladding features having a refractive index lower than a refractive index of said first cladding region, said plurality of lower-index cladding features arranged in no more than two layers; and

a core region surrounded by said first cladding region, said core region substantially surrounded by each layer of said no more than two layers, said plurality of lower-index 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 order N is less than or equal to 20, and

wherein said core region is configured to provide a loss for said all 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 all 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 plurality of lower-index cladding features has 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 plurality of lower-index cladding features are arranged in a single layer.

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 200 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.

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

10. A system comprising the optical amplifier of claim 9, wherein output pulse energy is in excess of 1 μ

J.

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

12. 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.

13. A fiber laser according to claim 12, wherein said fiber comprises a Nd doped fiber.

14. A fiber laser according to claim 12, wherein said fiber comprises a ytterbium doped fiber.

15. A chirped pulse amplification system for the amplification of picosecond or femtosecond pulses comprising the optical amplifier of claim 9 and a pulse compressor.

16. A laser micro-machining system comprising the chirped pulse amplification system of claim 15 and a positioning system.

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

18. The optical fiber of claim 1, wherein said order N is equal to 1.

19. The optical fiber of claim 1, wherein said order N is less than or equal to 3.

20. The optical fiber of claim 1, wherein said order N is less than or equal to 5.

21. The optical fiber of claim 1, wherein said order N is less than or equal to 10.

22. The optical fiber of claim 1, wherein said first cladding is discrete.

23. The chirped-pulse amplification system of claim 15, wherein said compressor comprises a fiber, and wherein said amplifier comprises a portion of a transmission fiber or a portion of said compressor or both.

24. The optical amplifier of claim 9, wherein said amplifier is a pulse amplifier to amplify picosecond, femtosecond, or nanosecond pulses.

25. The laser system of claim 12, further comprising an optical modulator disposed within said resonator to cause active or passive q-switching of said laser.

26. The laser system of claim 12 wherein said laser system is a CW system operating in the fundamental mode or few lowest order modes.

27. The optical fiber of claim 1, wherein at least one layer of said no more than two layers comprises a ring.

28. The optical fiber of claim 1, wherein at least one layer of said no more than two layers comprises two or more of said plurality of lower-index cladding features.

29. The optical fiber of claim 28, wherein said at least one layer comprises six or more of said plurality of lower-index cladding features.

30. The optical fiber of claim 1, wherein said plurality of lower-index cladding features are arranged in two layers.

31. The optical fiber of claim 30, wherein each of said two layers comprises a plurality of lower-index cladding features.

32. An optical rod for propagating lower order modes having order N or less and having a wavelength, λ

, while limiting propagation of all higher order modes with order greater than N by providing said all higher order modes with a higher loss than said lower order modes at said wavelength, λ

, said optical rod comprising;

a first cladding region comprising a plurality of lower-index cladding features, each of said plurality of lower-index cladding features having a refractive index lower than a refractive index of said first cladding region, said plurality of lower-index cladding features arranged in no more than two layers; and

a core region surrounded by the said first cladding region, said core region substantially surrounded by each layer of said no more than two layers, said plurality of lower-index 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 order N is less than or equal to 20, and

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

33. The rod of claim 32, wherein said core region is configured to provide a loss for said all higher order modes of at least about 1 dB.

34. The rod of claim 32, wherein said width of said core region is at least about 40 micrometers across.

35. The rod of claim 32, wherein said features have a minimum feature size, d, yielding a ratio of d/λ

that is at least about 10.

36. The rod of claim 32, 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 lower order modes to said higher order modes.

37. The optical fiber of claim 32, wherein said order N is equal to 1.

38. The optical fiber of claim 32, wherein said order N is less than or equal to 3.

39. The optical fiber of claim 32, wherein said order N is less than or equal to 5.

40. The optical fiber of claim 32, wherein said order N is less than or equal to 10.

41. The optical fiber of claim 32, wherein said first cladding is discrete.

42. The optical rod of claim 32, wherein at least one layer of said no more than two layers comprises a ring.

43. The optical rod of claim 32, wherein at least one layer of said no more than two layers comprises two or more of said plurality of lower-index cladding features.

44. The optical rod of claim 43, wherein said at least one layer comprises six or more of said plurality of lower-index cladding features.

45. The optical rod of claim 32, wherein said plurality of lower-index cladding features are arranged in a single layer.

46. The optical rod of claim 32, wherein said plurality of lower-index cladding features are arranged in two layers.

47. The optical rod of claim 46, wherein each of said two layers comprises a plurality of lower-index cladding features.

48. An optical fiber for propagating lower order modes having order N or less and having a wavelength, λ

, while limiting propagation of all higher order modes with order greater than N by providing said all higher order modes with a higher loss than said lower order modes at said wavelength, λ

, said optical fiber comprising;

a cladding further comprising a plurality of lower-index cladding features, each of said plurality of lower-index cladding features having a refractive index lower than a refractive index of said cladding, said plurality of lower-index cladding features arranged in no more than two layers; and

a core, said core substantially surrounded by each layer of said no more than two layers, said core having a width of at least about 20 micrometers,

wherein said order N is less than or equal to 20, and

wherein said fiber is configured such that (i) the lower order modes have no more than 1.0 dB of loss at a bending radius of about 30 centimeters and (ii) said all higher order modes have a loss of at least 0.5 dB.

49. The optical fiber of claim 48, wherein said order N is equal to 10.

50. The optical fiber of claim 48, wherein said order N is equal to 5.

51. The optical fiber of claim 48, wherein said order N is equal to 1.

52. The optical fiber of claim 51, wherein the fundamental mode has no more than 0.5 dB of loss at a bending radius of 10 centimeters.

53. The optical fiber of claim 48, wherein at least one layer of said no more than two layers comprises a ring.

54. The optical fiber of claim 48, wherein at least one layer of said no more than two layers comprises two or more of said plurality of lower-index cladding features.

55. The optical fiber of claim 53, wherein said at least one layer comprises six or more of said plurality of lower-index cladding features.

56. The optical fiber of claim 48, wherein said plurality of lower-index cladding features are arranged in a single layer.

57. The optical fiber of claim 48, wherein said plurality of lower-index cladding features are arranged in two layers.

58. The optical fiber of claim 57, wherein each of said two layers comprises a plurality of lower-index cladding features.