title: Modeling of transient modal instability in fiber amplifiers.
abstract: A model of transient modal instability in fiber amplifiers is presented. This model combines an optical beam propagation method that incorporates laser gain through local solution of the rate equations and refractive index perturbations caused by the thermo-optic effect with a time-dependent thermal solver with a quantum defect heating source term. This model predicts modal instability a fiber amplifier operating at 241, 270, and 287 Watts of output power characterized by power coupling to un-seeded modes, the presence of stable and unstable regions within the fiber, and rapid intensity variations along the fiber. The instability becomes more severe as the power is increased.
authors.affiliation: Laser and Optics Research Center, Department of Physics, United States Air Force Academy, 2354 Fairchild Drive Ste. 2A31, USAF Academy Colorado 80840, USA. benjamin.ward.1@us.af.mil
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Ward
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*; D007834:Lasers; D008962:Models, Theoretical