A 980-nm pump-induced nonlinear refractive-index (n_2) 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 copropagating and counterpropagating geometry. It was found that n_2 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 n_2. 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 as10 mW.
© 2005 Optical Society of America
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(060.2330) Fiber optics and optical communications : Fiber optics communications
(190.4370) Nonlinear optics : Nonlinear optics, fibers
Hernando Garcia, Anthony M. Johnson, Ferdinand A. Oguama, and Sudhir Trivedi, "Pump-induced nonlinear refractive-index change in erbium- and ytterbium-doped fibers: theory and experiment," Opt. Lett. 30, 1261-1263 (2005)