Physical Review A
Propagation-induced transition from slow to fast light in highly doped erbium fibers
Óscar G. Calderón, Sonia Melle, M. A. Antón, F. Carreño, Francisco Arrieta-Yáñez, E. Cabrera
Abstract
We analyze the propagation regime of an amplitude-modulated $1536\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ signal when traveling along a highly doped erbium fiber pumped at $977\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ as a function of the fiber length. A propagation-induced transition from superluminal to subluminal propagation takes place along the fiber length which allows a change in regime solely based upon increasing the signal modulation frequency. This peculiar behavior is due to the interplay between pump absorption and pump-power broadening of the spectral hole induced by coherent population oscillations. The effect of ion density on this frequency-dependent regime change has been investigated.