title: Low-threshold mode instability in Yb3+-doped few-mode fiber amplifiers.
abstract: Spatio-temporal instability of the fundamental mode in Yb(3+)-doped few-mode PM fiber amplifiers with a core diameter of 8.5 μm was registered at 2-30 Watts pump power. Both experimental and theoretical analysis revealed the nonlinear power transformation of the LP(01) fundamental mode into high-order modes. Numerical simulation revealed self-consistent growth of the higher-order mode and traveling electronic index grating accompanying the population grating induced by the mode interference field (due to different polarizability of the excited and unexcited Yb(3+) ions). Experimental results and numerical calculations showed the increase of the instability threshold along with an increase of the signal frequency bandwidth.
authors.forename: Maxim
authors.initials: M
authors.lastname: Kuznetsov
authors.forename: Oleg
authors.initials: O
authors.lastname: Vershinin
authors.forename: Valentin
authors.initials: V
authors.lastname: Tyrtyshnyy
authors.forename: Oleg
authors.initials: O
authors.lastname: Antipov
mesh_terms: D000669:Amplifiers, Electronic; D008962:Models, Theoretical; D055100:Optical Fibers; D012031:Refractometry; D012815:Signal Processing, Computer-Assisted; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D015018:Ytterbium