Multimode amplifier for amplifying single mode light

• US 7,576,909 B2
• Filed: 06/01/2005
• Issued: 08/18/2009
• Est. Priority Date: 07/16/1998
• Status: Expired due to Term

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Harter, Donald J., Fermann, Martin E.
• Primary Examiner(s): Hellner; Mark
• Application Number:
  US11/141,704
• Publication Number:
  US 20050243409A1
• Time in Patent Office: 1,539 Days
• Field of Search: 359/333, 359/341.1, 372/6, 385/124
• US Class Current: 359/333
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02F 1/3525 Optical damage
• CPC Class Codes: H01S 3/0606 with polygonal cross-section, e.g. slab, prism H01S3/0604 takes precedence
• CPC Class Codes: H01S 3/0615 Shape of end-face
• CPC Class Codes: H01S 3/0627 the resonator being monolithic, e.g. microlaser
• 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 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/094069 Multi-mode pumping
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/115 using intracavity electro-optic devices
• CPC Class Codes: H01S 3/1611 neodymium
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/1673 YVO4 [YVO]
• CPC Class Codes: H01S 3/302 in an optical fibre

Abstract

The invention describes techniques for the control of the spatial as well as spectral beam quality of multi-mode fiber amplification of high peak power pulses as well as using such a configuration to replace the present diode-pumped, Neodynium based sources. Perfect spatial beam-quality can be ensured by exciting the fundamental mode in the multi-mode fibers with appropriate mode-matching optics and techniques. The loss of spatial beam-quality in the multi-mode fibers along the fiber length can be minimized by using multi-mode fibers with large cladding diameters. Near diffraction-limited coherent multi-mode amplifiers can be conveniently cladding pumped, allowing for the generation of high average power. Moreover, the polarization state in the multi-mode fiber amplifiers can be preserved by implementing multi-mode fibers with stress producing regions or elliptical fiber cores. These lasers find application as a general replacement of Nd: based lasers, especially Nd:YAG lasers. Particularly utility is disclosed for applications in the marking, micro-machining and drilling areas.

Claims

1. An optical amplifier, comprising:

a single mode light source; and

a multimode fiber amplifier having a dopant concentration area within a core thereof which is smaller than a diameter of said core, such that said amplifier preferentially propagates single mode light.

7. An optical amplifier as claimed in any one of claims 1,2,3,4,5 and 6, further including a pump source for cladding-pumping said multimode fiber amplifier.

2. An optical amplifier, comprising:

a single mode light source;

means for coupling said single mode light into a multimode fiber amplifier; and

a core of said multimode fiber amplifier having a dopant profile such that gain is substantially confined to a fundamental mode propagating therethough.

3. An optical amplifier, comprising:

a single mode light source; and

a multimode fiber amplifier having a dopant profile wherein higher concentrations of dopant reside within a central region of a core thereof, as compared with that at peripheral regions of said core, to preferentially amplify single mode light.

4. An optical amplifier, comprising:

a single mode light source; and

a multimode fiber amplifier having a dopant concentration area within a region thereof which is smaller than a diameter of said core, to guide and amplify single mode light.

5. An optical amplifier, comprising:

a single mode light source; and

a multimode fiber amplifier having a dopant concentration area within a region thereof which is smaller than a diameter of said core, to preferentially amplify single mode light.

6. An optical amplifier, comprising:

a single mode light source;

means for coupling said single mode light into a multimode fiber amplifier; and

a core of said multimode fiber amplifier having a dopant profile wherein the doping is predominately at the center of said core and has a significantly smaller diameter than said core, such that said multimode fiber amplifier outputs predominately in a fundamental mode thereof.

8. An optical amplifier, comprising:

a single mode signal light source;

a pump light source; and

a multimode fiber amplifier having a dopant profile wherein higher concentrations of dopant reside within a central region of a core thereof, as compared with that at peripheral regions of said core, to preferentially amplify single mode signal light.

9. An optical amplifier, comprising:

a single mode signal light source;

a pump light source; and

means for coupling said single mode signal light into a multimode fiber amplifier; and

a core of said multimode fiber amplifier having a dopant profile such that gain is substantially confined to a fundamental mode propagating therethough.