Abstract

The pump/signal induced refractive index changes (RICs) could strongly affect the generation of light in fiber lasers and amplifiers. The RICs in cw or quasi-cw pumped rare-earth-doped optical fibers can be caused both by the thermal mechanisms (due to thermalization of the pumping energy) and a non-thermal effect due to population change of levels with a different polarizability (it can be described by Kramers-Kronning relation) [1-3]. Here we present the experimental study and theoretical analysis with the aim to compare the contributions of the thermal and electronic mechanisms to the RICs induced in the Yb-doped fiber amplifiers under different pumping conditions (cw or pulsed pumping) and amplifying signal behaviour.

© 2011 Optical Society of America