Pump-induced nonlinear refractive-index change in erbium- and ytterbium-doped fibers: theory and experiment.
A 980-nm pump-induced nonlinear refractive-index (n2) change in erbium-doped (20-m) and ytterbium-doped (20-m) fibers has been measured at 1064 nm by time-delayed photorefractive beam coupling in a co-propagating and counterpropagating geometry. It was found that n2 decreases at the wavelength of the probe beam when the pump beam is present. We present a semiclassical theory based on a four-state system that accounts for the pump-induced change of n2. Both theoretical and experimental results show that a significant index change, of the order of 10%, can be obtained for cw pump powers as small as 10 mW.
Department of Physics, Southern Illinois University, Edwardsville, Illinois 62026, USA.
Hernando
H
Garcia
Anthony M
AM
Johnson
Ferdinand A
FA
Oguama
Sudhir
S
Trivedi