Mode-locked multi-mode fiber laser pulse source

• US 8,873,593 B2
• Filed: 02/16/2001
• Issued: 10/28/2014
• Est. Priority Date: 11/25/1998
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Fermann, Martin E.
• Primary Examiner(s): SAYADIAN, HRAYR
• Application Number:
  US09/785,944
• Publication Number:
  US 20010024458A1
• Time in Patent Office: 5,002 Days
• Field of Search: 372/6, 372/18, 372/19, 372/5, 372/11, 372/25, 372/26, 372/31, 372/102, 372/22, 372/72, 372/23, 372/92, 372/27, 372/28, 385/28, 385/27, 385 45- 48
• US Class Current: 372/6
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/06704 Housings; Packages
• 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 3/06712 Polarising fibre; Polariser
• 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 3/06729 Peculiar transverse fibre profile
• CPC Class Codes: H01S 3/06733 Fibre having more than one cladding
• CPC Class Codes: H01S 3/06737 Fibre having multiple non-coaxial cores, e.g. multiple active cores or separate cores for pump and gain
• CPC Class Codes: H01S 3/06745 Tapering of the fibre, core or active region
• CPC Class Codes: H01S 3/06783 Amplifying coupler
• CPC Class Codes: H01S 3/08045 Single-mode emission
• CPC Class Codes: H01S 3/08054 Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation quarter-wave plates in a Q-switch laser H01S3/1124, H01S3/115
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/094019 Side pumped fibre, whereby pump light is coupled laterally into the fibre via an optical component like a prism, or a grating, or via V-groove coupling
• CPC Class Codes: H01S 3/094042 of a fibre laser
• CPC Class Codes: H01S 3/094069 Multi-mode pumping
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/1109 : Active mode locking
• CPC Class Codes: H01S 3/1115 : using intracavity saturable absorbers
• CPC Class Codes: H01S 3/1118 : Semiconductor saturable absorbers, e.g. semiconductor saturable absorber mirrors [SESAMs]; Solid-state saturable absorbers, e.g. carbon nanotube [CNT] based
• CPC Class Codes: H01S 3/1608 : erbium
• CPC Class Codes: H01S 3/1618 : ytterbium

Abstract

A laser utilizes a cavity design which allows the stable generation of high peak power pulses from mode-locked multi-mode fiber lasers, greatly extending the peak power limits of conventional mode-locked single-mode fiber lasers. Mode-locking may be induced by insertion of a saturable absorber into the cavity and by inserting one or more mode-filters to ensure the oscillation of the fundamental mode in the multi-mode fiber. The probability of damage of the absorber may be minimized by the insertion of an additional semiconductor optical power limiter into the cavity.

Claims

1. A laser, comprising:

a cavity which repeatedly passes light energy along a cavity axis;

a length of multi-mode optical fiber having a cladding and doped with a gain medium and positioned along said cavity axis;

a pump coupled to said cladding for exciting said gain medium; and

an optical guide positioned on said cavity axis which confines the light amplified by said multi-mode optical fiber to preferentially the fundamental mode of said multi-mode optical fiber.

2. A laser as defined in claim 1 additionally comprising a mode locking mechanism positioned on said cavity axis, wherein said mode locking mechanism comprises a passive mode locking element.

3. A laser as defined in claim 2 wherein said passive mode locking element comprises a saturable absorber.

4. A laser as defined in claim 3 wherein said saturable absorber comprises InGaAsP.

5. A laser as defined in claim 3 additionally comprising a power limiter for protecting said saturable absorber.

6. A laser as defined in claim 5 wherein said power limiter comprises a two photon absorber.

7. A method, comprising:

circulating light energy within a laser cavity;

amplifying said light energy within said laser cavity in a bent multi-mode fiber; and

confining said light energy within said laser cavity substantially to the fundamental mode of said multi-mode fiber.

8. A method as defined in claim 7 additionally comprising mode locking said light energy.