title: Optimizing single mode robustness of the distributed modal filtering rod fiber amplifier.
abstract: High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled from the outer fiber diameter. However, achieving ultra low NA for single mode (SM) guidance is challenging, thus different design strategies must be applied. The distributed modal filtering (DMF) design enables SM guidance in ultra low NA fibers with very large cores, where large preform tolerances can be compensated during the fiber draw. Design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes, which can cover a large fraction of the Yb emission band including wavelengths of 1030 nm and 1064 nm. Design parameters tolerating refractive index fabrication uncertainties of ± 10⁻⁴ are targeted to yield stable SM bandwidths.
authors.affiliation: DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark. mmajo@fotonik.dtu.dk
authors.forename: Mette Marie
authors.initials: MM
authors.lastname: Jørgensen
authors.forename: Sidsel Rübner
authors.initials: SR
authors.lastname: Petersen
authors.forename: Marko
authors.initials: M
authors.lastname: Laurila
authors.forename: Jesper
authors.initials: J
authors.lastname: Lægsgaard
authors.forename: Thomas Tanggaard
authors.initials: TT
authors.lastname: Alkeskjold
mesh_terms: D000669:Amplifiers, Electronic; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D005374:Filtration / Q000295:instrumentation*; D007834:Lasers; D008027:Light; D008962:Models, Theoretical; D012542:Scattering, Radiation