Open AccessOrigin of thermal modal instabilities in large mode area fiber amplifiers
Author(s) -
Benjamin G. Ward,
Craig Robin,
Iyad Dajani
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.011407
Subject(s) - modal , instability , optics , fiber , optical fiber , mode volume , thermal , amplifier , single mode optical fiber , physics , mode (computer interface) , polarization maintaining optical fiber , mechanics , materials science , fiber optic sensor , computer science , optoelectronics , thermodynamics , cmos , polymer chemistry , composite material , operating system
We present a dynamic model of thermal modal instability in large mode area fiber amplifiers. This model allows the pump and signal optical intensity distributions to apply a time-varying heat load distribution within the fiber. This influences the temperature distribution that modifies the optical distributions through the thermo-optic effect thus creating a feedback loop that gives rise to time-dependent modal instability. We describe different regimes of operation for a representative fiber design. We find qualitative agreement between simulation results and experimental results obtained with a different fiber including the time-dependent behavior of the instability and the effects of different cooling configurations on the threshold. We describe the physical processes responsible for the onset of the instability and suggest possible mitigation approaches.