Compact ultra-short pulse source amplifiers

• US 9,553,421 B2
• Filed: 10/16/2013
• Issued: 01/24/2017
• Est. Priority Date: 10/16/2012
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Fermann, Martin E.
• Primary Examiner(s): BOLDA, ERIC L
• Application Number:
  US14/571,367
• Publication Number:
  US 20150311666A1
• Time in Patent Office: 1,196 Days
• US Class Current: 1/1
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: H01J 49/161 using photoionisation, e.g. by laser
• 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 3/06708 Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering optical fibres as passive waveguides G02B6/02
• CPC Class Codes: H01S 3/06725 Fibre characterized by a specific dispersion, e.g. for pulse shaping in soliton lasers or for dispersion compensating [DCF]
• CPC Class Codes: H01S 3/06741 Photonic crystal fibre, i.e. the fibre having a photonic bandgap
• 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 3/08013 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 3/094026 for synchronously pumping, e.g. for mode locking
• CPC Class Codes: H01S 3/094042 of a fibre laser
• CPC Class Codes: H01S 3/094061 Shared pump, i.e. pump light of a single pump source is used to pump plural gain media in parallel
• 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 3/109 Frequency multiplication, e.g. harmonic generation
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers

Abstract

The present invention relates to compact, low noise, ultra-short pulse sources based on fiber amplifiers, and various applications thereof. At least one implementation includes an optical amplification system having a fiber laser seed source producing seed pulses at a repetition rate corresponding to the fiber laser cavity round trip time. A nonlinear pulse transformer, comprising a fiber length greater than about 10 m, receives a seed pulse at its input and produces a spectrally broadened output pulse at its output, the output pulse having a spectral bandwidth which is more than 1.5 times a spectral bandwidth of a seed pulse. A fiber power amplifier receives and amplifies spectrally broadened output pulses. A pulse compressor is configured to temporally compress spectrally broadened pulses amplified by said power amplifier. Applications include micro-machining, ophthalmology, molecular desorption or ionization, mass-spectroscopy, and/or laser-based, biological tissue processing.

Claims

1. An optical amplification system, comprising:

a fiber laser seed source producing seed pulses at a repetition rate corresponding to the fiber laser cavity round trip time, said seed source producing seed pulses having a pulse width greater than about 5 picoseconds (ps);

a nonlinear pulse transformer comprising a fiber having a length greater than about 10 m, said pulse transformer receiving a ps seed pulse at its input and producing a spectrally broadened ps output pulse at its output, said ps output pulse having a spectral bandwidth which is more than 1.5 times a spectral bandwidth of a ps seed pulse, wherein a pulse input to said nonlinear pulse transformer is stretched by less than a factor of ten in said pulse transformer;

a Yb;

fiber power amplifier receiving and amplifying said spectrally broadened ps output pulse said power amplifier producing amplification near 1000 nm and arranged with a pump source for one or both of cladding pumping or core pumping at a pump wavelength of about 980 nm; and

a pulse compressor configured to temporally compress spectrally broadened pulses amplified by said power amplifier.

2. An optical amplification system according to claim 1, wherein said nonlinear pulse transformer comprises a fiber having length greater than about 20 m and less than 3000 m.

3. An optical amplification system according to claim 1, wherein said seed source generates a pulse width greater than 10 ps.

4. An optical amplification system according to claim 1, wherein a pulse width generated with said ps seed source is compressible to a pulse width less than 5 ps.

5. An optical amplification system according to claim 1, wherein said nonlinear pulse transformer spectrally broadens a pulse injected to its input by a factor >

2.

6. An optical amplification system according to claim 1, wherein said nonlinear pulse transformer spectrally broadens a pulse injected to its input by a factor >

4.

7. An optical amplification system according to claim 1, said amplification system further comprising a down counter.

8. An optical amplification system according to claim 1, wherein said nonlinear pulse transformer comprises lengths of amplifier fiber and passive undoped fiber.

9. An optical amplification system according to claim 1, wherein said fiber seed source comprises a modelocked fiber laser.

10. An optical amplification system according to claim 1, wherein said pulse compressor comprises at least one of a fiber Bragg grating, a bulk grating, prism, grism, a section of bulk material, a photonic crystal fiber or a Kagome fiber.

11. An optical amplification system according to claim 1, said amplification system further comprising an undoped fiber inserted after the power amplifier configured to spectrally broaden the pulses coupled out of the power amplifier.

12. An optical amplification system according to claim 1, wherein said amplification system is further configured to substantially optimize the pulse quality of the pulses coupled out of the pulse compressor by insertion of elements with optimized values of 3^rd and 4^th order dispersion.

22. An optical amplification system according to claim 1, wherein said amplification system is configured as an element of a system for laser-based, biological tissue processing.

25. The optical amplification system of claim 1, wherein said pulse transformer comprises a length of Yb:

amplifier fiber, and said pump source is configured to pump said length of Yb;

amplifier fiber.

26. The optical amplification system of claim 25, wherein said pulse transformer is arranged with a succession of relatively short amplifier fiber sections with longer lengths of dispersive fibers located between the amplifier fiber sections.

27. The optical amplification system of claim 26, wherein the sections are interconnected via fiber splices to form a substantially integral pulse transformer.

28. The optical amplification system of claim 26, wherein the fibers of said pulse transformer each have overall positive dispersion.

13. An optical amplification system, comprising:

a fiber laser seed source producing seed pulses at a repetition rate corresponding to the fiber laser cavity round trip time;

a nonlinear pulse transformer, said pulse transformer receiving picosecond (ps) pulses at its input and producing a spectrally broadened ps output pulse at its output, said ps output pulse having a spectral bandwidth which is more than 1.5 times a spectral bandwidth of a ps seed pulse, wherein a pulse input to said nonlinear pulse transformer is stretched by less than a factor of ten in said pulse transformer;

a Yb;

fiber power amplifier which receives and amplifies said spectrally broadened pulse to produce a pulse energy greater than about 5 μ

J, said power amplifier producing amplification near 1000 nm and arranged with a pump source for one or both of cladding pumping or core pumping at a pump wavelength of about 980 nm; and

a pulse compressor configured to temporally compress spectrally broadened pulses amplified by said power amplifier.

14. An optical amplification system according to claim 13, wherein said nonlinear pulse transformer comprises a fiber having a length greater than about 20 m and less than 3000 m.

15. An optical amplification system according to claim 13, wherein said seed source generates a pulse width >

10 ps.

16. An optical amplification system according to claim 13, wherein a pulse width generated with said ps seed source is compressible to a pulse width less than 5 ps.

17. An optical amplification system according to claim 13, said amplification system further comprising a down counter.

18. An optical amplification system according to claim 13, wherein said nonlinear pulse transformer comprises lengths of amplifier fiber and passive undoped fiber.

19. An optical amplification system according to claim 13, wherein said fiber seed source comprises a modelocked fiber laser.

20. An optical amplification system according to claim 13, wherein said pulse compressor comprises at least one of a fiber Bragg grating, a bulk grating, prism, grism, a section of bulk material, a photonic crystal fiber or a Kagome fiber.

21. An optical amplification system according to claim 13, said amplification system further comprising an undoped fiber inserted after the power amplifier configured to spectrally broaden the pulses coupled out of the power amplifier.

29. The optical amplification system of claim 13, wherein said pulse transformer comprises a length of Yb:

amplifier fiber, and said pump source is configured to pump said length of Yb;

amplifier fiber.

30. The optical amplification system of claim 29, wherein said pulse transformer is arranged with a succession of relatively short amplifier fiber sections with longer lengths of dispersive fibers located between the amplifier fiber sections.

31. The optical amplification system of claim 30, wherein the sections are interconnected via fiber splices to form a substantially integral pulse transformer.

32. The optical amplification system of claim 30, wherein the fibers of said pulse transformer each have overall positive dispersion.

23. An optical amplification system, comprising:

a ps noise seed source, said noise seed source producing incoherent or partially coherent pulses with a pulse width greater than about 10 ps;

a nonlinear pulse transformer, said pulse transformer receiving a ps pulse at its input and producing a spectrally broadened ps pulse at its output, wherein a pulse input to said nonlinear pulse transformer is stretched by less than a factor of ten in said pulse transformer;

a nonlinear Yb;

fiber power amplifier, said nonlinear power amplifier producing amplification near 1000 nm and arranged with a pump source for one or both of cladding pumping or core pumping at a pump wavelength of about 980 nm; and

a compressor configured to temporally compress spectrally broadened pulses amplified by said nonlinear power amplifier.

24. The amplification system of claim 23, wherein said incoherent or partially coherent pulses are generated by a fiber-based modelocked laser, a semiconductor mode locked laser, a Fourier domain mode locked laser, or a gain-switched laser diode.

33. The optical amplification system of claim 23, wherein said pulse transformer comprises a length of Yb:

amplifier fiber, and said pump source is configured to pump said length of Yb;

amplifier fiber.

34. The optical amplification system of claim 33, wherein said pulse transformer is arranged with a succession of relatively short amplifier fiber sections with longer lengths of dispersive fibers located between the amplifier fiber sections.

35. The optical amplification system of claim 34, wherein the sections are interconnected via fiber splices to form a substantially integral pulse transformer.

36. The optical amplification system of claim 34, wherein the fibers of said pulse transformer each have overall positive dispersion.