IN-LINE, HIGH ENERGY FIBER CHIRPED PULSE AMPLIFICATION SYSTEM

• US 20070273960A1
• Filed: 08/10/2007
• Published: 11/29/2007
• Est. Priority Date: 06/03/2003
• Status: Active Grant

• Current Assignee: Donald Harter, Gennady Imeshev, Ingmar Hartl, Martin Fermann
• Original Assignee: Donald Harter, Gennady Imeshev, Ingmar Hartl, Martin Fermann
• Inventors: Harter, Donald, Fermann, Martin, Imeshev, Gennady, Hartl, Ingmar
• Granted Patent: US 7,518,788 B2
• Time in Patent Office: Days
• US Class Current: 359/333
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• 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 3/0085 Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/06712 Polarising fibre; Polariser
• CPC Class Codes: H01S 3/06725 Fibre characterized by a specific dispersion, e.g. for pulse shaping in soliton lasers or for dispersion compensating [DCF]
• 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 3/10015 by monitoring or controlling, e.g. attenuating, the input signal

Abstract

By writing non-linear chirp into fiber Bragg gratings, greater control over dispersion compensation in chirped pulse amplification (CPA) systems is obtained, such that, for example, the dispersion profile of the fiber Bragg grating and a bulk compressor may be matched. An iterative method of writing the fiber grating can reduce the group delay ripple to very low levels; and adaptive control of the fiber grating dispersion profile can further reduce these levels, while in addition offering greater acceptable yield in the manufacture of such gratings. Fiber Bragg gratings may be designed so as to provide customized pulse shapes optimized for various end uses, such as micromachining, for example, and may also be used to counteract gain-narrowing in a downstream amplifier.

Claims

1. A chirped pulse amplification system comprising:

a low group delay ripple nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps;

at least one fiber amplifier following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50 to produce compressed pulses having a bandwidth greater than 1 nm.

2. A chirped pulse amplification system as in claim 1, wherein the pulse stretcher system is configured to produce stretched pulses having a group delay ripple less than about 10 ps.

3. A chirped pulse amplification system as in claim 1, wherein the pulse stretcher system is configured to produce stretched pulses having a group delay ripple less than about 2 ps.

4. A chirped pulse amplification system as in claim 1, wherein said pulse stretcher system is configured to produce stretched pulses longer than 300 ps.

5. A chirped pulse amplification system as in claim 1, wherein said pulse stretcher system is configured to produce stretched pulses longer than 1 ns.

6. A chirped pulse amplification system as in claim 5, wherein said pulse compressor is configured to compress said stretched pulses by more than a factor of 150.

7. A chirped pulse amplification system as in claim 5, wherein said compressed pulses have an energy greater than 1 μ

J.

8. A chirped pulse amplification system as in claim 1, wherein said pulse stretcher system includes plural concatenated fiber Bragg grating stretchers.

9. A chirped pulse amplification system as in claim 1, wherein said pulse compressor comprises at least one fiber Bragg grating compressor and a bulk grating compressor.

10. A chirped pulse amplification system as in claim 1, wherein the compressed pulses are output at a target downstream from said pulse compressor, where an optical beam-path between said pulse compressor and said target further includes additional optical elements comprising material other than air.

11. A chirped pulse amplification system as in claim 10, wherein said additional optical elements comprise optical beam delivery fibers.

12. A chirped pulse amplification system as in claim 11, wherein said delivery fibers comprise at least one of a single-mode fiber, a multi-mode fiber operated with a single-mode output, a holey fiber, a photonic crystal fiber, or a fiber with a guiding air-hole core.

13. A chirped pulse amplification system as in claim 1, further comprising an adaptively controlled pulse shaper located up-stream of said at least one fiber amplifier and configured to pre-compensate for self-phase modulation in said at least one fiber amplifier.

14. A chirped pulse amplification system comprising:

a low group delay ripple nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps;

at least one diode laser amplifier, parametric amplifier, Raman amplifier, or combination thereof following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50 to produce compressed pulses having a bandwidth greater than 1 nm.

15. A chirped pulse amplification system as in claim 14, wherein the pulse stretcher system is configured to produce stretched pulses having a group delay ripple less than about 10 ps.

16. A chirped pulse amplification system as in claim 14, wherein the pulse stretcher system is configured to produce stretched pulses having a group delay ripple less than about 2 ps.

17. An optical combination comprising:

a seed pulse source configured to produce optical pulses with a spectral bandwidth greater than 1 nm;

a nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to exhibit a group delay ripple of less than about 10 ps within the spectral bandwidth of said seed pulse source; and

an amplifier following said pulse stretcher system.

18. An optical combination as in claim 17, wherein the group delay ripple is less than about 2 ps.

19. An optical combination as in claim 17, further comprising a compressor for recompressing stretched pulses.

20. A chirped pulse amplification system comprising:

a seed pulse source for producing short optical pulses;

a stretcher for stretching said pulses;

a plurality of concatenated sections of predominantly polarization maintaining fiber, at least one of which is also an amplifier; and

at least one polarizer inserted between any two sections of said predominantly polarization maintaining fiber.

21. A chirped pulse amplification system comprising:

at least one low group delay ripple nonlinearly chirped fiber Bragg grating pulse stretcher for producing stretched pulses;

at least one fiber amplifier following said pulse stretcher; and

a pulse compressor for compressing said stretched pulses to produce compressed pulses having an energy greater than 100 nJ and a bandwidth greater than 1 nm.

22. A chirped pulse amplification system as claimed in claim 21, wherein said pulse stretcher is configured to produce stretched pulses having a group delay ripple less than about 10 ps.

23. A chirped pulse amplification system as claimed in claim 21, wherein said pulse stretcher is configured to produce stretched pulses having a group delay ripple less than about 2 ps.

24. A chirped pulse amplification system as claimed in claim 21, wherein said pulse compressor includes at least one chirped fiber Bragg grating and a bulk grating.

25. A chirped pulse amplification system as claimed in claim 21, wherein said pulse compressor comprises a holey or photonic bandgap fiber.

26. A chirped pulse amplification system as claimed in claim 25, wherein the holey or photonic bandgap fiber is engineered to perform complete pulse compression or partial pulse compression.

27. A chirped pulse amplification system as claimed in claim 26, wherein the holey or photonic bandgap fiber which performs complete or partial pulse compression also acts as power delivery fiber.

28. A chirped pulse amplification system comprising:

a short pulse seed source;

a fiber grating pulse stretcher;

an adaptive pulse shaper;

at least one amplifier; and

a pulse compressor.

29. A chirped pulse amplification system according to claim 28, wherein said at least one amplifier is at least one of a fiber, Raman, parametric, solid-state, or diode amplifier.

30. A chirped pulse amplification system according to claim 28, wherein said adaptive pulse shaper is an adaptive fiber grating based pulse shaper.

31. A chirped pulse amplification system according to claim 28, wherein said fiber grating pulse stretcher and said adaptive pulse shaper are combined into one integrated fiber grating pulse shaping device.

32. A chirped pulse amplification system according to claim 31, wherein adaptive pulse shaping in said pulse shaping device is enabled via modifying a refractive index of at least one selectable portion of said pulse shaping device by controlling a temperature of said selectable portion.

33. A chirped pulse amplification system as claimed in claim 32 wherein a number of said selectable portions is in a range between 4 and 4000.

34. A chirped pulse amplification system as claimed in claim 32, wherein a number of said selectable portions is in a range between 4 and 400.

35. A chirped pulse amplification system according to claim 31, wherein adaptive pulse shaping in said pulse shaping device is enabled via modifying a refractive index of at least one selectable portion of said pulse shaping device by controlling an internal stress within said selectable portion.

36. A chirped pulse amplification system as claimed in claim 35 wherein a number of said selectable portions is in a range between 4 and 4000.

37. A chirped pulse amplification system as claimed in claim 35 wherein a number of said selectable portions is in a range between 4 and 400.

38. A chirped pulse amplification system comprising:

a low group delay ripple nonlinearly chirped fiber Bragg grating pulse stretcher;

at least one fiber amplifier following said pulse stretcher and having a substantially step index profile; and

a pulse compressor for compressing stretched pulses to produce compressed pulses having a bandwidth greater than 1 nm.

39. A chirped pulse amplification system as in claim 38, wherein the pulse stretcher is configured to exhibit a group delay ripple less than about 10 ps.

40. A chirped pulse amplification system as in claim 38, wherein the pulse stretcher is configured to exhibit a group delay ripple less than about 2 ps.

41. A chirped pulse amplification system comprising:

a fiber Bragg grating pulse stretcher, said pulse stretcher configured to produce stretched pulses or pulse trains with a prescribed, but freely selectable, amplitude and phase profile;

at least one amplifier following said pulse stretcher; and

a pulse compressor for compressing said stretched pulses,

whereby the system is capable of producing output pulses or output pulse trains with a freely selectable amplitude profile.

42. A chirped pulse amplification system according to claim 41, wherein said freely selectable amplitude profile is produced at a target material, and

wherein an optical beam path between a bulk compressor and said target material includes optical material other than air, the optical material comprising bulk optical materials, optical delivery fibers, or a combination thereof

43. A chirped pulse amplification system according to claim 41, wherein said output pulses or output pulse trains are used for micro-structuring or micro-machining of a target material, and wherein said freely selectable amplitude profile is selected for the micro-structuring properties of said target material.

44. A chirped pulse amplification system according to claim 41, wherein said freely selectable amplitude profile generated by said pulse stretcher is used to counteract gain-narrowing in said at least one amplifier down-stream from said pulse stretcher, such that the amplified pulse width after compression in said pulse compressor is minimized.

45. A chirped pulse amplification system comprising:

a fiber Bragg grating pulse stretcher system including a plurality of fiber Bragg gratings, each of the gratings designed to stretch a separate spectral component of an input pulse;

at least one amplifier following said pulse stretcher system; and

a pulse compressor system for compressing and reconstructing stretched pulses by incoherent addition.

46. A system as claimed in claim 45 wherein said pulse compressor system comprises a series of bulk compressors spaced so as to temporally reconstruct said input pulse.

47. A system as claimed in claim 45, wherein said pulse compressor system comprises one or more bulk compressors spaced so as to output temporally separated portions of said input pulse.

48. A chirped pulse amplification system comprising:

a nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps;

at least one fiber amplifier following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50 to produce compressed pulses.

49. A chirped pulse amplification system as in claim 48, wherein said compressed pulses have a bandwidth greater than 1 nm.

50. A chirped pulse amplification system comprising:

a nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps and including plural concatenated fiber Bragg grating stretchers;

at least one amplifier following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50.

51. A chirped pulse amplification system comprising:

a nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps;

at least one amplifier following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50 wherein compressed pulses are obtained at a target downstream from said pulse compressor, and

wherein an optical beam-path between said pulse compressor and said target includes additional optical elements comprising material other than air.

52. A chirped pulse amplification system comprising:

a nonlinearly chirped fiber Bragg grating pulse stretcher system, said pulse stretcher system configured to produce stretched pulses longer than 100 ps;

at least one amplifier following said pulse stretcher system; and

a pulse compressor configured to compress said stretched pulses by more than a factor of 50; and

an adaptively controlled pulse shaper located up-stream of said at least one amplifier, in order to pre-compensate for self-phase modulation in said at least one amplifier.