Multimode Fabry-Perot fiber laser

Patent metadata

Field	Value
Publication number	US-9647410-B2
Application number	US-201514958059-A
Country	US
Kind code	B2
Filing date	Dec 3, 2015
Priority date	Jun 3, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A multimode (“MM”) fiber oscillator is configured with MM active fiber doped with light emitters, a pair of MM passive fibers spliced to respective opposite ends of the MM active fiber, and a plurality of MM fiber Bragg gratings (“FBG”) written in respective cores of the MM passive fibers to provide a resonant cavity. The passive and active fibers are configured with respective cores which are dimensioned with respective diameters matching one another and substantially identical numerical apertures.

First claim

The invention claimed is:

1. An CW or QCW multimode (“MM”) Fabri-Perot all fiber oscillator comprising:
a MM active fiber provided with a monolithic core which is doped with light emitters;
two MM passive fibers spliced to respective opposite ends of the MM active fiber; and
MM fiber Bragg gratings (“FBG”) written in respective cores of the MM passive fibers and defining a resonant cavity therebetween, wherein the laser is configured to output light emitted at a desired wavelength and having a narrow linewidth which varies between 0.02 and 10 nm.

2. The MM fiber oscillator of claim 1 , wherein the MM active and passive fibers are configured with respective monolithic cores, the cores having respective opposing ends dimensioned with respective diameters which substantially match one another.

3. The MM fiber oscillator of claim 2 , wherein the core of the MM active fiber has a cylindrical cross-section with a uniform diameter between opposite ends thereof or double-bottleneck-shaped cross section.

4. The MM fiber oscillator of claim 1 , wherein the MM active and passive fibers are configured with respective numerical apertures substantially matching one another.

5. The MM fiber oscillator of claim 1 further comprising a pump operative to side-pump the MM active fiber, the pump including one or a plurality of MM laser diodes.

6. The MM fiber oscillator of claim 1 , wherein the light emitters include ions of rare earth elements which are selected from the group consisting of ytterbium (“Yb”), erbium (“Er”), neodymium (“Nd”), thulium (“Tm”), holmium (“Ho”), praseodymium (“Pr”), cerium (“Ce”) yttrium (Y 3+ ), samarium (Sm 3+ ), europium (Eu 3+ ), gadolinium (Gd 3+ ), terbium (Tb 3+ ), dysprosium (Dy 3+ ), and lutetium (Lu 3+ ) and combinations of these.

7. The MM fiber oscillator of claim 1 , wherein the MM FBGs include high and low reflectivity fiber gratings defining therebetween a resonant cavity.

8. The MM fiber oscillator of clam 7 , wherein the upstream MM passive fiber with the high reflectivity FBG is configured to guide light which leaks through the high reflectivity FBG back into the resonant cavity.

9. The MM fiber oscillator of claim 1 further comprising a combiner coupled to the downstream MM passive fiber, the upstream MM passive fiber being configured to guide light which leaks through the high reflectivity FBG to the combiner, wherein the combiner receives a free end of the upstream MM passive fiber to combined the light exiting the resonant cavity through the low reflectivity FBG and the leaked light.

10. The MM fiber oscillator of claim 1 further comprising a mirror provided on a faucet of the upstream MM passive fiber, the mirror being configured to reflect light leaking through the high reflectivity FBG back into the cavity.

11. A fiber laser system comprising at least one gain block configured with:
a MM active fiber doped with ions of one or more rare-earth elements;
a pair of MM passive fibers spliced to respective opposite ends of the MM active fiber;
spaced high reflectivity and low MM fiber Bragg gratings (“FBG”) written in respective cores of the MM passive fibers and defining a resonant cavity therebetween, wherein the MM active, passive and FBGs define a MM Fabri-Perot laser; and
a pump operative to side-pump the active fiber, wherein the fiber laser system is configured to output one or more kW-level light emitted at a desired wavelength and having a narrow spectral linewidth which at least one order of magnitude smaller than that of a single mode laser which operates at a same power as the MM Fabri-Perot laser.

12. The fiber laser system of claim 11 , wherein the pump is configured with a plurality of laser diodes and operative to output a train of pulses.

13. The fiber laser system of claim 12 , wherein a MM output of the gain block is pulsed, the output light pulses each having a substantially uniform power level over an entire duration of the pulse.

14. The MM fiber laser system of claim 11 , wherein the MM active and passive fibers are configured with respective cores, the cores having respective opposing ends dimensioned to have substantially matching diameters.

15. The MM fiber laser system of claim 11 , wherein the MM active and passive fibers are configured with respective numerical apertures substantially matching one another.

16. The MM fiber laser system of claim 11 , wherein the gain block is configured to emit a continuous output.

17. The MM fiber laser system of claim 11 further comprising a combiner coupled to a downstream MM passive fiber formed with the low reflectivity FBG, an upstream MM passive fiber being configured to guide light which leaks through the high reflectivity FBG to the combiner, wherein the combiner receives a free end of the upstream MM passive fiber to combine the light exiting the resonant cavity through the low reflectivity and high reflectivity FBGs.

18. The MM fiber laser system of claim 11 , wherein an upstream MM passive fiber having the high reflectivity FBG has a free end provided with a reflective element configured to backreflect light leaking though the high reflectivity FBG back into the resonant cavity.

19. The MM fiber laser system of claim 14 , wherein the core of the MM active fiber has a cylindrical cross-section with a uniform diameter between opposite ends thereof or double-bottleneck-shaped cross section.

20. The MM fiber laser system if claim 11 , wherein the narrow spectral line varies between 0.02 and 10 nm.

Assignees

• Ipg Photonics Corp

Inventors

• Mashkin Andrey
• Shcherbina Fedor

Classifications

• H01S3/0804

  Transverse or lateral modes · CPC title

• H01S3/0675 Primary

  Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers · CPC title

• H01S3/06708

  Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering (optical fibres as passive waveguides G02B6/02) · CPC title

• H01S3/1618

  ytterbium · CPC title

• H01S3/09415

  the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping · CPC title