title: Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry.
abstract: Spatially resolved spectral interferometry is used to measure the mode content of a Yb-doped photonic-crystal fiber rod amplifier with a 2300 μm(2) mode area. The technique, known as S(2) imaging, was adapted for the short fiber amplifier at full power and revealed a small amount of a copolarized LP(11) mode. Simulations illustrate the potential for weak mode suppression in this fiber and agree qualitatively with the measurements of S(2) and M(2). Higher-order-mode content depends on the alignment of the input signal at injection and ranged from -18 dB for optimized alignment to -13 dB when the injection alignment was offset along the LP(11) axis by 30% of the 55 μm mode-field diameter.
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, New York 14623-1299, USA. jbro@lle.rochester.edu
authors.forename: Jake
authors.initials: J
authors.lastname: Bromage
authors.forename: John M
authors.initials: JM
authors.lastname: Fini
authors.forename: Christophe
authors.initials: C
authors.lastname: Dorrer
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Zuegel