title: Single-Mode ytterbium-doped Large-Mode-Area photonic bandgap rod fiber amplifier.
abstract: Enabling Single-Mode (SM) operation in Large-Mode-Area (LMA) fiber amplifiers and lasers is critical, since a SM output ensures high beam quality and excellent pointing stability. In this paper, we demonstrate and test a new design approach for achieving SM LMA rod fibers by using a photonic bandgap structure. The structure allows resonant coupling of higher-order modes from the core and acts as a spatially Distributed Mode Filter (DMF). With this approach, we demonstrate passive SM performance in an only ~50 cm long and straight ytterbium-doped rod fiber. The amplifier has a mode field diameter of ~59 µm at 1064 nm and exhibits a pump absorption of 27 dB/m at 976 nm.
authors.affiliation: NKT Photonics, Blokken 84, 3460 Birkerød, Denmark. tta@nktphotonics.com
authors.forename: Thomas Tanggaard
authors.initials: TT
authors.lastname: Alkeskjold
authors.forename: Marko
authors.initials: M
authors.lastname: Laurila
authors.forename: Lara
authors.initials: L
authors.lastname: Scolari
authors.forename: Jes
authors.initials: J
authors.lastname: Broeng