title: Novel technique for mode selection in a multimode fiber laser.
abstract: A simple technique for transverse mode selection in a large-mode-area (multimode) fiber laser is described. The technique exploits the different spectral responses of feedback elements based on a fiber Bragg grating and a volume Bragg grating to achieve wavelength-dependent mode filtering. This approach has been applied to a cladding-pumped thulium-doped fiber laser with a multimode core to achieve a single-spatial-mode output beam with a beam propagation factor (M2) of 1.05 at 1923 nm. Without mode selection the free-running fiber laser has a multimode output beam with an M2 parameter of 3.3. Selective excitation of higher order modes is also possible via the technique and preliminary results for laser oscillation on the LP11 mode are also discussed along with the prospects for scaling to higher power levels.
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ, UK. jmod1g09@orc.soton.ac.uk
authors.forename: J M O
authors.initials: JM
authors.lastname: Daniel
authors.forename: J S P
authors.initials: JS
authors.lastname: Chan
authors.forename: J W
authors.initials: JW
authors.lastname: Kim
authors.forename: J K
authors.initials: JK
authors.lastname: Sahu
authors.forename: M
authors.initials: M
authors.lastname: Ibsen
authors.forename: W A
authors.initials: WA
authors.lastname: Clarkson
mesh_terms: D005246:Feedback; D005336:Fiber Optic Technology / Q000295:instrumentation* / Q000379:methods*; D005857:Germanium / Q000737:chemistry; D007834:Lasers; D008962:Models, Theoretical; D055100:Optical Fibers; D013932:Thulium / Q000737:chemistry*
chemical_list: D005857:Germanium; D013932:Thulium