Hybrid short-pulse amplifiers with phase-mismatch compensated pulse stretchers and compressors

• US 5,847,863 A
• Filed: 04/25/1996
• Issued: 12/08/1998
• Est. Priority Date: 04/25/1996
• Status: Expired due to Term

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Hariharan, Anand, Galvanauskas, Almantas, Harter, Donald J.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/637,956
• Time in Patent Office: 957 Days
• Field of Search: 359/333, 359/337, 359/341, 359/345
• US Class Current: 359/341.3
• 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 3/2316 Cascaded amplifiers
• CPC Class Codes: H01S 3/235 Regenerative amplifiers

Abstract

Disclosed is a system for amplification of ultrashort optical pulses. The disclosed system has reduced size and increased robustness, reliability and cost-effectiveness. The disclosed invention is particularly effective in chirped pulse amplification (CPA) systems wherein pulses are stretched, amplified, and re-compressed. According to one aspect of the invention a compact stretcher is used with a bulk compressor, and compatibility between them is achieved by inserting a telescope in the path of the collimated beam. Alternatively, compatibility between the stretcher and the compressor is achieved by creating nonlinearly chirped bragg grating in the fiber stretcher. According to another aspect of the invention, a fiber and a bulk amplifiers are used to amplify the pulse, and compatibility between them is achieved by inserting a doubling crystal in the path of the pulse between the two amplifiers. Another aspect of the disclosed amplification system is the pumping of a laser amplifier with a laser pump of the same material as the laser amplifier, but operating under different conditions.

Claims

1. A system for amplification of short optical pulses, comprising:

a compact stretcher receiving light pulses and outputting stretched light pulses therefrom;

an optical amplifier receiving the stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom, said compressor having at least one light path wherein the amplified pulse is collimated, and comprising a lens arrangement inserted in said light path, said lens arrangement preserving collimation of said amplified pulse.

2. The system for amplification of short optical pulses as claimed in claim 1, wherein said compressor comprises a collimating diffraction grating and a reflector, and wherein the lens arrangement is situated in a light path between the diffraction grating and the reflector.

3. The system for amplification of short optical pulses as claimed in claim 2, wherein said diffraction grating is transmissive.

4. The system for amplification of short optical pulses as claimed in claim 2, wherein said diffraction grating is reflective.

5. The system for amplification of short optical pulses as claimed in claim 1, wherein said stretcher comprises fiber grating.

6. The system for amplification of short optical pulses as claimed in claim 1, wherein said stretcher comprises dispersion fiber.

7. The system for amplification of short optical pulses as claimed in claim 6, wherein said dispersion fiber further comprises a reflecting element at an end thereof.

8. The system for amplification of short optical pulses as claimed in claim 7, wherein said reflecting element is a faraday rotating mirror.

9. A system for amplification of short optical pulses, comprising:

a selfphase modulation fiber

an optical amplifier receiving stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom, said compressor having at least one light path wherein the amplified pulse is collimated, and comprising a lens arrangement inserted in said light path, said lens arrangement preserving collimation of said amplified pulse.

10. A system for producing short optical pulses, comprising:

a compact injection source producing light pulses;

an optical amplifier receiving the light pulse and outputting amplified pulses therefrom;

a compressor receiving the amplified pulses and outputting compressed pulses, said compressor having at least one collimated light path, and comprising a lens arrangement inserted in said collimated light path, wherein said lens arrangement preserves collimation.

11. The system for producing short optical pulses as recited in claim 10, wherein said compact injection source comprises a tunable laser diode.

12. The system for producing short optical pulses as recited in claim 10, wherein said compact injection source comprises an oscillator producing short light pulses and a compact stretcher for stretching the short light pulses.

13. The system for producing short optical pulses as recited in claim 10, wherein said compact injection source comprises a compact stretcher for stretching received light pulses, and wherein said system further comprises a compact compressor inserted between said optical amplifier and said compressor for pre-compressing light pulses received from said optical amplifier and sending the pre-compressed light pulses to said compressor.

14. A system for amplification of short optical pulses, comprising:

a stretcher receiving light pulses and outputting stretched light pulses therefrom, said stretcher having at least one collimated light path, and wherein said stretcher comprises a lens arrangement inserted in said collimated light path;

an optical amplifier receiving the stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom;

wherein said lens arrangement preserves collimation of light passing therethrough.

15. The system for amplification of short optical pulses as claimed in claim 14, wherein said stretcher comprises a collimating diffraction grating and a reflector, and wherein the lens arrangement is situated in a light path between the diffraction grating and the reflector.

16. The system for amplification of short optical pulses as claimed in claim 15, wherein said diffraction grating is transmissive.

17. The system for amplification of short optical pulses as claimed in claim 15, wherein said diffraction grating is reflective.

18. A system for amplification of short optical pulses, comprising:

a stretcher receiving light pulses and outputting stretched light pulses therefrom;

a nonlinear group velocity dispersion compensator, said compensator having at least one collimated light path, and comprising a lens arrangement inserted in said collimated light path;

an optical amplifier receiving the light pulses from said compensator and outputting compensated amplified light pulses;

a compressor receiving the compensated amplified light pulses and outputting compressed light pulses therefrom

wherein said lens arrangement preserves collimation of said light pulses passing therethrough.

19. The system for amplification of short optical pulses as claimed in claim 18, wherein said compensator comprises one of a transmissive diffraction element and a transmissive dispersion element, and wherein the telescope is situated in a light path between the diffraction element and the reflector.

39. The system for amplification of short optical pulses as claimed in claim 18, further comprising a second optical amplifier for amplifying the stretched light pulses received from said stretcher.

20. A system for amplification of short optical pulses, comprising:

a stretcher receiving light pulses and outputting stretched light pulses therefrom, said stretcher comprising a nonlinearly chirped fiber grating;

an optical amplifier receiving the stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom.

21. A method for compensating nonlinear group velocity dispersion mismatch between a stretcher and a compressor in a system for amplification of short optical pulses, said method comprising inserting at least one lens arrangement in a spatially chirped collimated beam in one of said stretcher and compressor, wherein the lens arrangement preserves collimation of light passing therethrough.

22. A method for compensating nonlinear group velocity dispersion mismatch between a stretcher and a compressor in a system for amplification of short optical pulses, said method comprising creating a nonlinearly chirped Bragg grating in said stretcher.

23. An apparatus for amplifying stretched ultrashort pulses, comprising:

a first gain media having a predefined amplification band;

a second gain media having a predefined amplification band which does not overlap the amplification band of said first gain media;

a nonlinear optical crystal inserted in a light path between said first and second gain media for achieving wavelength matching between said first and second gain media.

24. In an apparatus for amplifying stretched ultrashort pulses, said apparatus comprising a first gain media having a predefined amplification band and a second gain media having a predefined amplification band which does not overlap the amplification band of said first gain media, a method for achieving wavelength matching between said first and second gain media, said method comprising inserting a nonlinear optical crystal in a light path between said first and second gain.

25. An optical amplification system, comprising:

a laser amplifier operating at a first set of predetermined conditions;

a pump laser consisting essentially of the same material as the amplifier and operating under a second set of predetermined operating conditions different from said first set of operating conditions to thereby emit light at a shorter wavelength than said amplifier and match an absorption band of said amplifier.

27. The optical amplification system of claim 25, wherein the laser amplifier is an alexandrite regenerative amplifier operating at a first temperature, and said pump laser is a pump alexandrite laser operating at a second temperature elevated from said first temperature.

29. The optical amplification system of claim 25, wherein the laser amplifier is an erbium doped fiber amplifier and said pump laser is an erbium doped fiber pump laser, and wherein said fiber amplifier have an absorption cross section at a lasing wavelength of the pump laser, and wherein said fiber amplifier produces an emission cross section which is lower than said absorption cross section.

33. The optical amplification system of claim 29, wherein said pump fiber is Q-switched laser pump.

26. A method for operating an optical amplification system, said optical amplification system comprising a laser amplifier and a pump laser consisting essentially of the same material as the amplifier, the method comprising:

operating said laser amplifier at a first set of predetermined conditions;

operating said pump laser under a second set of predetermined operating conditions different from said first set of operating conditions to thereby cause said pump laser to emit light at a shorter wavelength than said amplifier and to match an absorption band of said amplifier.

28. The method of operating an optical amplification system according to claim 26, wherein the gain medium is an alexandrite regenerative amplifier, and said pump laser is a pump alexandrite laser, and wherein said first set of operating condition comprises operating said amplifier laser at a temperature elevated from room temperature and wherein said second set of operating condition comprises operating said pump laser at room temperature.

30. The method for operating an optical amplification system as claimed in claim 26, wherein the gain medium is an erbium doped fiber amplifier, and said pump is a pumped fiber, and wherein said first set of operating conditions and said second set of operating conditions are predefined to cause said fiber amplifier to have an absorption cross section at a lasing wavelength of the pump laser, and a to further cause said fiber amplifier to produce an emission cross section which is lower than said absorption cross section.

31. The method for operating an optical amplification system as claimed in claim 30, wherein said first set of operating conditions comprises doping said fiber amplifier to a first level of doping and wherein said second set of operating conditions comprises doping said pumped fiber to a second level of doping different from said first level.

32. The method for operating an optical amplification system as claimed in claim 30, wherein said first set of operating conditions comprises doping said fiber amplifier using a predefined doping content and wherein said second set of operating conditions comprises doping said pumped fiber using a second predefined doping content different from said first predefined doping content.

34. The method for operating an optical amplification system as claimed in claim 30, wherein said pump fiber is Q-switched pump laser.

35. An optical amplification system, comprising:

a switched regenerative amplifier receiving light pulses and amplifying said light pulses;

a doubling crystal for doubling the frequency of said light pulses before said light pulses enter said regenerative amplifier;

means for splitting said light signals after said light signals pass through said doubling crystal but before said light pulses enter said regenerative amplifier, to thereby produce a main beam and a secondary beam of said light pulse;

means for diverting said secondary beam for operating a switch of said switched regenerative amplifier.

36. An optical amplification system, comprising:

an oscillator for producing light pulses having a defined frequency;

a stretcher for stretching said light pulses;

a compact amplifier for amplifying said light pulses received from said stretcher;

a doubling crystal receiving said light pulses from said compact amplifier and doubling the frequency of said light pulses;

a bulk amplifier receiving said light pulses from said doubling crystal and amplifying said light pulses;

a compressor receiving said light pulses from said bulk amplifier and compressing said light pulses.

37. The optical amplification system of claim 36, wherein said bulk amplifier comprises:

a regenerative Alexandrite laser amplifier;

pump Alexandrite laser;

wherein the output of said pump Alexandrite laser is fed into said regenerative Alexandrite laser amplifier.

38. The optical amplification system of claim 37, wherein said regenerative Alexandrite laser amplifier includes an electro-optical switch, and wherein said system further comprises:

a beam spliter for splitting said light pulses and defining plurality of light paths, wherein light pulses from one of said light paths enters said regenerative Alexandrite laser amplifier and light pulses of another one of said light paths are used to switch said electro-optical switch.

40. A system for amplification of short optical pulses, comprising:

a stretcher receiving light pulses and outputting stretched light pulses therefrom;

an optical amplifier receiving the stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom, said compressor comprising a nonlinearly chirped fiber grating.

41. A system for amplification of short optical pulses, comprising:

a stretcher receiving light pulses and outputting stretched light pulses therefrom;

an optical amplifier receiving the stretched light pulses and outputting amplified light pulses therefrom;

a compressor receiving the amplified light pulses and outputting compressed light pulses therefrom;

a group velocity dispersion compensator comprising a nonlinearly chirped fiber grating.

42. An optical amplification system, comprising:

an oscillator for producing light pulses having a defined frequency;

a stretcher for stretching said light pulses;

a compact amplifier for amplifying said light pulses received from said stretcher;

a beam splitter for splitting said light pulses;

a bulk amplifier comprising an electro-optical switch responsive to light pulses from said beam spliter.

43. A system for producing short optical pulses, comprising:

a compact injection source producing light pulses;

an optical amplifier for amplifying said optical pulses;

a nonlinear group velocity dispersion compensator, said compensator having at least one collimated light path, and comprising a lens arrangement inserted in said collimated light path;

a compressor receiving the compensated amplified light pulses and outputting compressed light pulses therefrom.