title: Theoretical analysis of mode instability in high-power fiber amplifiers.
abstract: We present a simple theoretical model of transverse mode instability in high-power rare-earth doped fiber amplifiers. The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo-optic effect, leading to transverse mode instability. The temporal and spectral characteristics of the instability dynamics are investigated, and it is shown that the instability can be seeded by both quantum noise and signal intensity noise, while pure phase noise of the signal does not induce instability. It is also shown that the presence of a small harmonic amplitude modulation of the signal can lead to generation of higher harmonics in the output intensity when operating near the instability threshold.
authors: Department of Photonics Engineering, Technical University of Denmark Bldg. 345v, DK-2800 Kgs. Lyngby, Denmark. kryh@fotonik.dtu.dk
authors: Kristian Rymann
authors: KR
authors: Hansen
authors: Thomas Tanggaard
authors: TT
authors: Alkeskjold
authors: Jes
authors: J
authors: Broeng
authors: Jesper
authors: J
authors: Lægsgaard
mesh_terms: D000669:Amplifiers, Electronic; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D008962:Models, Theoretical; D055100:Optical Fibers