Environmentally stable passively modelocked fiber laser pulse source

• US 5,923,686 A
• Filed: 06/16/1997
• Issued: 07/13/1999
• Est. Priority Date: 12/20/1993
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.), Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: IMRA America Incorporated (Aisin Corp.), Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Harter, Donald J., Fermann, Martin E.
• Primary Examiner(s): Bovernick, Rodney
• Assistant Examiner(s): Wise, Robert E.
• Application Number:
  US08/876,933
• Time in Patent Office: 757 Days
• Field of Search: 372/18, 372/11, 372/6
• US Class Current: 372/18
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/08059 Constructional details of the reflector, e.g. shape mirrors in general G02B5/08; mountings for mirrors G02B7/18
• CPC Class Codes: H01S 3/1112 Passive mode locking
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

The present invention is directed to providing an environmentally stable, ultra-short pulse source. Exemplary embodiments relate to passively modelocked ultra-short fiber lasers which are insensitive to temperature variations and which possess only negligible sensitivity to pressure variations. Further, exemplary embodiments can be implemented in a cost-effective manner which render them commercially practical in unlimited applications. Arbitrary fiber lengths (e.g., on the order of 1 millimeter to 1 kilometer, or greater) can be used to provide an ultra-short pulse with a cost-effective architecture which is commercially practical.

Claims

1. A passively modelocked laser comprising:

a laser energy generator having a cavity which includes;

a gain medium for amplifying energy in the cavity;

a pair of reflectors which define an optical axis which passes through the gain medium;

a compensator which reduces the effects of linear phase drifts of the gain medium; and

a polarization beam splitter for coupling output laser energy from said cavity.

2. A passively modelocked laser according to claim 1, wherein said compensator further includes:

a polarization controller within said cavity.

3. A passively modelocked laser according to claim 2, wherein said polarization controller further includes:

a first Faraday rotator; and

a second Faraday rotator, said first and second Faraday rotators located within said cavity to define an intra-cavity fiber region of said cavity.

4. A passively modelocked laser according to claim 3, wherein said cavity further includes:

a lens focusing energy generated along said axis.

5. A passively modelocked laser according to claim 1, wherein said pair of reflectors further includes:

a first cavity mirror located at a first end of said cavity;

a second cavity mirror located at a second end of said cavity opposite said first end, said second cavity mirror further including a Faraday rotator.

6. A passively modelocked laser according to claim 1, wherein said cavity further includes:

a highly-birefringent fiber; and

low-birefringent fiber operably connected with said highly-birefringent fiber for transmitting laser energy along said axis of said cavity.

7. A passively modelocked laser according to claim 6, wherein said gain medium includes highly-birefringent fiber.

8. A passively modelocked laser according to claim 1, wherein said cavity further includes:

a linear energy polarization transformer in said cavity.

9. A passively modelocked laser according to claim 8, wherein said linear energy polarization transformer includes:

a waveplate located along said axis for introducing a linear phase delay.

10. A passively modelocked laser according to claim 9, comprising:

a fiber isolator located adjacent said polarization beam splitter.

11. A passively modelocked laser according to claim 1, wherein said laser energy outputting means further includes:

a fiber isolator in the path of output energy from said cavity.

12. A passively modelocked laser according to claim 1, further comprising:

a pump coupled to said laser energy generator, said pump further including;

an energy source; and

a wavelength-division multiplexing coupler for coupling said pump to said cavity.

13. A passively modelocked laser according to claim 12 wherein said wavelength division multiplexing coupler includes low-birefringent fiber.

14. A passively modelocked laser according to claim 1, wherein said gain medium is a highly-birefringent, rare-earth fiber.

15. A passively modelocked laser according to claim 14, wherein said rare-earthed fiber has an arbitrary fiber length.

16. A passively modelocked laser according to claim 1, wherein said cavity is a linear cavity.

17. A passively modelocked laser according to claim 1, further comprising:

a fiber isolator for output coupling of laser light from the cavity.

18. A passively modelocked laser according to claim 1, wherein said compensator further includes:

at least one Faraday rotator for rotating polarized light along said axis.

19. A passively modelocked laser according to claim 1, further comprising:

a saturable absorber formed as a semiconductor grown on a substrate structure for initiating modelocking of the laser.

20. A passively modelocked laser according to claim 1, further comprising:

a fiber stretcher for initiating modelocking of the laser.

21. A passively modelocked laser according to claim 1, further comprising:

a movable mirror for initiating modelocking of the laser.

22. A passively modelocked laser according to claim 1 additionally comprising an optical filter within said cavity.