Modular fiber-based chirped pulse amplification system

• US 20050226286A1
• Filed: 03/31/2004
• Published: 10/13/2005
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Gu, Xinhua, Harter, Donald J., Cho, Gyu Choen, Ulrich, Otho E. Jr., Liu, Zhenlin
• Granted Patent: US 7,711,013 B2
• Time in Patent Office: Days
• US Class Current: 372/25
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• 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 3/0064 Anti-reflection devices, e.g. optical isolaters absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/0085 Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/02 Constructional details housings or packages of fibre lasers H01S3/06704
• CPC Class Codes: H01S 3/025 of solid state lasers, e.g. housings or mountings
• CPC Class Codes: H01S 3/06704 Housings; Packages
• CPC Class Codes: H01S 3/06712 Polarising fibre; Polariser
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094011 with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/1001 by controlling the optical pumping
• CPC Class Codes: H01S 3/1028 by controlling the temperature
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/13013 by controlling the optical pumping
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/2316 : Cascaded amplifiers
• CPC Class Codes: H01S 5/0612 : controlled by temperature
• CPC Class Codes: H01S 5/06804 : by monitoring an external parameter, e.g. temperature

Abstract

A modular ultrafast pulse laser system is constructed of individually pre-tested components manufactured as modules. The individual modules include an oscillator, pre-amplifier and power amplifier stages, a non-linear amplifier, and a stretcher and compressor. The individual modules can typically be connected by means of simple fiber splices.

Claims

1. A pulse laser system composed of a plurality of replaceable modules, comprising;

an ultrafast oscillator module;

a nonlinear amplifier module receiving the oscillator output and amplifying the signal while broadening its spectral width;

an isolator module for eliminating feedback into the oscillator;

a stretcher module for temporally stretching the output of said isolator/polarizer oscillator;

a linear pre-amplifier module for amplifying the stretched output;

a down-counter module for controlling the repetition rate of the laser system;

a power amplifier module for amplifying the output of the down-counter module; and

a compressor for temporally shortening the output of said power amplifier module.

5. A system as claimed in claim 1, wherein ASE is spectrally separated from the signal by one or more said said compressor and at least one of said amplifiers.

6. A system as claimed in claim 1 or 2, wherein an attenuator module which attenuates the oscillator output is located between said oscillator and said non-linear amplifier;

and PM-PM splices are used to join said modules.

7. A system as claimed in claim 1 or 2, further including tap modules between selected ones of said modules.

8. A system as claimed in claim 1 or 2, further including polarization modules located between selected ones of said modules.

9. A system as claimed in claim 1 or 2, wherein said down-counter module comprises an AOM, and additionally serves as a bandwidth filter.

10. A system as claimed in claim 1, further including a spectral filter between said oscillator module and said nonlinear amplifier.

11. A system as claimed in claim 1, wherein said preamplifier has a gain bandwidth narrower than the spectrum from the non-linear amplifier, to spectrally filter the output from said non-linear amplifier, said non-linear amplifier shifting ASE to shorter wavelengths away from the signal.

12. A system as claimed in claim 1 or 2, wherein said power amplifier includes a diode-based pump, and serves as a spectral filter.

14. A system as claimed in claim 1 or 2, wherein the pulse signal output from said compressor is in the fs regime.

2. A pulse laser system composed of a plurality of replaceable modules, comprising;

an ultrafast oscillator module;

a stretcher module for temporally stretching the output of said oscillator module;

a spectral filter module placed before or after said stretcher module;

an amplifier module receiving the stretched output and amplifying the signal;

an isolator module;

a linear pre-amplifier module for amplifying the signal;

a down-counter module for controlling the repetition rate of the laser system;

a power amplifier module for amplifying the output of the down-counter module; and

a compressor for temporally shortening the output of said power amplifier module.

3. A system as claimed in claim 2, wherein said source is an ultrafast oscillator, and further including isolator means for isolating said oscillator from a first of said amplifier stages to a level of at least 35 dB.

13. A system as claimed in claim 2, wherein said oscillator produces a relatively broad spectrum output above approximately the 10 nm range, and wherein an attenuator module attenuates the oscillator output.

4. A pulse laser system, comprising the following components:

a signal source;

a stretcher for temporally stretching an output of said source;

a fiber amplifier; and

a compressor for recompressing an output of said amplifier; and

an AOM for selecting output pulses from said amplifier;

wherein each of said components is provided as a pre-tested module, and said system is constructed by connecting said modules via simple fiber splices.

15. An all-fiber chirped pulse amplifier system composed of a plurality of modular optical subassemblies, comprising;

at least an oscillator module, a stretcher module, an amplifier module and a compressor module, each subject to separate assembly and test, and coupled into the system by a fiber splice;

tap units selectively located between ones of said modules for test, monitoring or feedback; and

means between selected ones of said modules for improving fidelity of the polarization state.

16. A pulse laser system, comprising;

a signal source;

a stretcher for temporally stretching an output of said source;

a fiber amplifier; and

a compressor for recompressing an output of said amplifier; and

an AOM for selecting output pulses from said amplifier and serving as a bandwidth filter.

17. A pulse laser system, comprising;

a signal source;

a stretcher for temporally stretching an output of said source;

at least one fiber amplifier stage; and

a compressor for recompressing an output of a final amplifier stage; and

wherein a length of one of said amplifier stages is selected to remove ASE at the lasing wavelength, and said compressor serving as a spectral filter.

18. A system as claimed in claim 17, further including an AOM for selecting output pulses from one of said amplifier stages.

19. A system as claimed in claim 17, wherein said signal source is an ultrafast oscillator, and further including filter means for spectral matching between said oscillator and a first of said amplifier stages.

20. A system as claimed in claim 17, wherein said signal source is an ultrafast oscillator, and further including isolator means for isolating said oscillator from a first of said amplifier stages to a level of at least 35 dB.

25. A system as claimed in claim 17, where said length is approximately 4 m.

21. A chirped-pulse amplification system, comprising;

a signal source;

a stretcher module;

at least one amplifier stage, including a non-linear amplifier module and a linear amplifier module;

a compressor module; and

wherein said non-linear amplifier broadens the spectrum of the signal by at least a factor of 2 by self-phase modulation, and said linear amplifier serves as a spectral filter by a mechanism including at least gain narrowing.

22. A system as claimed in claim 21, wherein said compressor module further operates as a spectral filter.

23. A chirped-pulse amplification system, comprising;

an ultrafast oscillator signal source;

at least one amplifier stage;

a compressor module; and

at least one isolator module between said oscillator and a first of said amplifier stages for providing at least 35 dB isolation therebetween.

24. A chirped-pulse amplification system, comprising;

an ultrafast oscillator module;

at least one amplifier module;

a down-counter module;

a compressor module; and

means between selected ones of said modules for improving fidelity of the polarization state.

35. A system as claimed in claim 24, wherein said means between selected ones of said modules comprises a polarizer module which contains at least a polarizer unit tunable to reject light propagating in an unwanted polarization state.

36. A system as claimed in claim 35, wherein one or more of said polarizer modules contain one or more isolator units.

26. An active stabilization system for a fiber amplification system, comprising:

a power amplifier including a gain fiber,

a pump source for said power amplifier,

means for directing a portion of the pump light from said pump source into a monitor fiber identical to or equivalent to said gain fiber, so as to clone a temperature dependent spectrum of said gain fiber; and

feedback means for controlling a parameter of said pump source so as to match the pump source wavelength with an absorption spectrum of the gain fiber.

27. A system as claimed in claim 26, wherein said directing means comprises a tap unit.

28. A system as claimed in claim 26, wherein said directing means includes means for collecting scattered or spurious pump light from said pump source.

29. A system as claimed in claim 26, wherein said controlled parameter is a temperature of said pump source.

30. A system as claimed in claim 26, wherein said monitor fiber is said gain fiber.

31. A system as claimed in claim 26, wherein said gain fiber and said monitor fiber are in substantially or fully in thermal contact with one another.

32. A system as claimed in claim 26, wherein said power amplifier is side-pumped.

33. A chirped-pulse amplification system, comprising;

a signal source;

at least one amplifier module;

a compressor module; and

an AOM module located within said amplification system and operating as a pulse deflector, said deflector introducing spatial dispersion; and

said compressor module comprising a bulk grating compressor compensating for said spatial dispersion.

34. A system as claimed in claim 33, wherein said AOM deflector serves as one stage of said compressor.