Inexpensive variable rep-rate source for high-energy, ultrafast lasers

• US 9,553,417 B2
• Filed: 10/17/2013
• Issued: 01/24/2017
• Est. Priority Date: 05/14/2003
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Harter, Donald J.
• Primary Examiner(s): Park, Kinam
• Application Number:
  US14/056,052
• Publication Number:
  US 20160322771A1
• Time in Patent Office: 1,195 Days
• Field of Search: 372/6
• US Class Current: 1/1
• CPC Class Codes: G02B 6/2932 comprising a directional router, e.g. directional coupler, circulator
• CPC Class Codes: G02B 6/29374 in an optical light guide G02B6/02214 takes precedence
• 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 3/067 Fibre lasers
• 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 3/06716 Fibre compositions per se C03C13/04or doping with active elements lasing materials in general H01S3/14
• 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 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/08013 Resonator comprising a fibre, e.g. for modifying dispersion or repetition rate the active medium being a fibre H01S3/067
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/10046 Pulse repetition rate control H01S3/11 takes precedence
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/115 using intracavity electro-optic devices
• CPC Class Codes: H01S 3/1608 erbium
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA
• CPC Class Codes: H01S 3/2375 : Hybrid lasers H01S3/07 takes precedence
• CPC Class Codes: H01S 5/0057 : for temporal shaping, e.g. pulse compression, frequency chirping
• CPC Class Codes: H01S 5/0085 : for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/06216 : Pulse modulation or generation
• CPC Class Codes: H01S 5/12 : the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18
• CPC Class Codes: H04B 10/508 : Pulse generation, e.g. generation of solitons

Abstract

System for converting relatively long pulses from rep-rate variable ultrafast optical sources to shorter, high-energy pulses suitable for sources in high-energy ultrafast lasers. Fibers with positive group velocity dispersion (GVD) and self phase modulation are advantageously employed with the optical sources. These systems take advantage of the need for higher pulse energies at lower repetition rates so that such sources can be cost effective.

Claims

1. A system comprising:

a source of optical pulses;

a fiber having positive group-velocity dispersion (GVD) at a wavelength of said source, wherein said positive GVD has a negative value of dispersion when expressed in the units ps/nm/km, said fiber configured to receive said optical pulses and to induce self-phase modulation (SPM) to said optical pulses, wherein said fiber produces output pulses compressible to pulse widths of about 10 ps or less; and

a pump source for pumping said source of optical pulses.

2. The system of claim 1, wherein said source of optical pulses comprises a mode-locked fiber laser.

3. The system of claim 1, wherein said source of optical pulses generates pulses at a variable repetition rate.

4. The system of claim 1 wherein said fiber comprises a rare-earth doped amplifier fiber having said GVD and inducing said SPM.

5. The system of claim 1, wherein said system comprises a chirped fiber Bragg grating disposed downstream from said fiber.

6. The system of claim 5, wherein said chirped fiber Bragg grating is arranged as a portion of a pulse compressor.

7. The system of claim 1, further comprising a pulse compressor disposed downstream from said fiber.

8. The system of claim 7, wherein said pulse compressor comprises a bulk grating compressor.

9. The system of claim 1, wherein said pump source comprises at least one pump laser diode.

10. The system of claim 1, wherein said source of optical pulses comprises a microchip laser.

11. The system of claim 10, wherein said microchip laser is arranged for q-switching.

12. The system of claim 1, wherein said optical source comprises a cw laser diode and an optical modulator, wherein said cw laser diode is selectively gated to generate said optical pulses at a repetition rate in the kHz to MHz regime, said modulator providing an extinction ratio in the range from 20-30 dB.

13. The system according to claim 1, wherein said fiber comprises a coreless end cap, whereby a mode is expanded before an end surface of said fiber.

14. The system according to claim 1, wherein said system comprises a conversion crystal for varying the wavelength of an output of said system.

15. The system according to claim 1, wherein said fiber comprises a multimode fiber configured to propagate a single mode beam.

16. The system according to claim 1, wherein said fiber comprises a holey fiber.

17. The system according to claim 1, wherein said fiber comprises a Yb gain fiber configured as a Yb fiber amplifier.

18. A system comprising:

a source of optical pulses;

a first optical amplifier disposed downstream from said source of optical pulses and arranged to amplify said optical pulses;

a fiber having positive group velocity dispersion (GVD) at a wavelength of said source of optical pulses, wherein positive said GVD has a negative value of dispersion when expressed in the units ps/nm/km, said fiber arranged to receive an output of said first optical amplifier and to induce self-phase modulation (SPM) to the output of said amplifier, wherein said fiber produces output pulses compressible to pulse widths of about 10 ps or less; and

a pump source for pumping said source of optical pulses.

19. The system of claim 18, further comprising a first compressor receiving a compressible output from said fiber with positive GVD and producing a compressed output pulse.

20. The system of claim 18, wherein said first optical amplifier comprises a fiber amplifier.

21. The system of claim 18, wherein said optical source generates pulses at a repetition rate in the range from about 1 kHz to 1 MHz.

22. The system of claim 18, wherein said optical source comprises a cw laser diode and an optical modulator, wherein said cw laser diode is selectively gated to generate said optical pulses at a repetition rate in the kHz to MHz regime, said modulator providing an extinction ratio in the range from 20-30 dB.

23. The system as claimed in claim 18, further comprising a second amplifier arranged to amplify an output of said fiber having positive GVD.

24. The system as claimed in claim 23, wherein said second amplifier operates as a parabolic pulse amplifier.

25. The system of claim 23, further comprising a conversion crystal for varying the wavelength of an output of said system.

26. The system of claim 18, further comprising a conversion crystal for varying the wavelength of an output of said system.

27. The system of claim 18, further comprising a two-stage compressor arranged to receive an output of said fiber with positive GVD, wherein said two stage compressor comprises a second fiber with positive GVD and self-phase modulation.

28. The system of claim 18, wherein said fiber comprises a coreless end cap, whereby a mode is expanded before an end surface of said fiber.

29. The system of claim 18, wherein one or both of said fiber or said fiber amplifier comprises a multimode fiber configured to propagate a single mode beam.

30. The system of claim 18, wherein said fiber comprises a holey fiber.

31. The system of claim 18, wherein said fiber comprises a Yb gain fiber configured as a Yb fiber amplifier.