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

• US 10,014,645 B2
• Filed: 11/21/2016
• Issued: 07/03/2018
• Est. Priority Date: 05/14/2003
• Status: Expired due to Term

• 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:
  US15/356,845
• Publication Number:
  US 20170077669A1
• Time in Patent Office: 589 Days
• 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 pulse source outputting pulses which are less than or equal to approximately 10 ns at a variable repetition rate in a range from about 1 kHz to less than about 10 MHz, said pulse source comprising;

a light source; and

a fiber amplifier with positive group-velocity dispersion (GVD) at an emission wavelength of said light source, said fiber amplifier receiving an output of said light source, and causing spectral broadening in said fiber amplifier,

wherein said fiber amplifier is one of a multimode fiber or a holey fiber,

wherein said positive GVD has a negative value of dispersion when expressed in units of ps/nm/km, and

wherein said light source comprises a q-switched microchip laser outputting pulses having a pulse energy equal to or greater than 500 nJ.

2. The system as claimed in claim 1, wherein said microchip laser outputs pulses greater than 1 ps.

3. The system as claimed in claim 1, wherein said microchip laser outputs pulses in a range from about 50 ps to about 10 ns.

4. The system as claimed in claim 1, wherein said fiber is a multimode fiber operably arranged for single mode operation and to generate self-phase modulation, wherein said fiber comprises a coreless end cap, wherein a mode is expanded before a surface of said fiber.

5. The system as claimed in claim 1, wherein pulse energies are greater than 1 μ

J and said pulses are stretched at an output of the fiber amplifier.

6. The system as claimed in claim 1, further comprising:

a pulse compressor receiving an output of said multimode fiber amplifier.

7. The system as claimed in claim 1, wherein said fiber amplifier comprises a doped, multimode amplifier fiber.

19. The system as claimed in claim 1, wherein said spectral broadening is caused by self-phase modulation.

8. A system comprising:

a light source, wherein said light source comprises a cw laser diode configured to be gated by switching it on and off;

an optical modulator arranged to receive the output of said light source and outputting pulses with a duration less than or equal to 10 ns at a repetition rate in a range from kHz to MHz, wherein said modulator is disposed at an output of said cw laser diode;

a first amplifier arranged to amplify pulses output by said modulator; and

a fiber with positive group velocity dispersion (GVD) at a wavelength of said cw laser diode, wherein positive GVD has a negative value of dispersion when expressed in the units ps/nm/km, and

wherein said fiber is arranged to receive an output of said amplifier and to induce spectral broadening to the output of said amplifier.

9. The system as claimed in claim 8, further comprising a first compressor receiving a compressible output from said fiber with positive GVD and producing a compressed output pulse.

10. The system as claimed in claim 8, wherein said first amplifier is a fiber amplifier.

11. The system according to claim 8, wherein said repetition rate is in the range from 1 kHz to 1 MHz.

12. The system according to claim 8, wherein a wavelength of said cw laser diode is 1.0 μ

m or is in the telecom window at 1550 nm.

13. The system according to claim 8, wherein an extinction ratio of said modulator is in the range from 20-30 dB.

14. The system as claimed in claim 8, further comprising a second amplifier arranged to amplify an output of said fiber with positive GVD.

15. The system as claimed in claim 8, further comprising a conversion crystal for varying the wavelength of an output of said system.

16. The system as claimed in claim 8, 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.

17. The system as claimed in claim 16, wherein said two-stage compressor comprises a four-port circulator and two fiber gratings.

18. The system as claimed in claim 14, wherein said second amplifier operates as a parabolic pulse amplifier.

20. The system as claimed in claim 8, wherein said spectral broadening is caused by self-phase modulation.