Multi-mode fiber amplifier

• US 8,761,211 B2
• Filed: 04/25/2003
• Issued: 06/24/2014
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Fermann, Martin E., Harter, Donald J.
• Primary Examiner(s): SAYADIAN, HRAYR
• Application Number:
  US10/424,220
• Publication Number:
  US 20030202547A1
• Time in Patent Office: 4,078 Days
• Field of Search: 372/6, 372/5, 372/18, 372/21, 372/26, 372/22, 372/31, 372/101, 372/102, 372/26.31, 372/70, 372/91, 372/92, 385/27, 385/28, 385/127, 385/12, 359/341.3, 359/345
• 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 light amplifier for amplifying light from a near-diffraction-limited laser source, the light amplifier comprising:

a length of multi-mode optical fiber, said multi-mode optical fiber including a gain medium;

a length of single-mode optical fiber optically coupled to the length of multi-mode optical fiber, a fundamental mode of said multi-mode fiber matched to the mode of the single mode fiber,

an energy source for exciting said gain medium, said energy source arranged for side pumping said optical fiber, and

an input optically coupled to said multi-mode fiber, said input comprising a near-diffraction-limited laser source providing a nearly diffraction limited input beam having a signal wavelength, said input comprising said length of single-mode optical fiber, said multi-mode fiber providing an output beam having the signal wavelength that is amplified by said gain medium, wherein said output beam having the signal wavelength is substantially in the fundamental mode at an output of said light amplifier,

wherein said light amplifier is configured to provide a peak output power greater than 10 KW for the output beam having the signal wavelength.

2. The light amplifier of claim 1, wherein said input comprises a section of tapered fiber.

3. The light amplifier of claim 2, wherein an output mode from the tapered fiber is matched to the fundamental mode of the multi-mode fiber.

4. The light amplifier of claim 1, said near-diffraction limited laser source comprising a cw fiber laser.

5. The light amplifier of claim 1, wherein said light amplifier provides a peak output power greater than 20 KW/amplifier length for the output beam having the signal wavelength.

6. The light amplifier of claim 1, wherein said multi-mode optical fiber comprises a core, said gain medium is concentrated centrally in said core, and wherein mode-coupling into higher-order modes is reduced by gain-guiding and the fundamental mode is preferentially amplified.