title: Modulation-frequency-controlled change from sub- to superluminal regime in highly doped erbium fibers.
abstract: We report a change from sub- to superluminal propagation upon increasing the modulation frequency of an amplitude-modulated 1,550 nm signal when propagating through highly doped erbium fibers pumped at 980 nm. We show that the interplay between the pump absorption and the pump-power broadening of the spectral hole induced by coherent population oscillations may drastically affect the fractional advancement or delay of the signal for the considered fibers.
authors.affiliation: Escuela Universitaria de Optica, Universidad Complutense de Madrid, C/ Arcos de Jalón s/n, 28037 Madrid, Spain. smelle@fis.ucm.es
authors.forename: Sonia
authors.initials: S
authors.lastname: Melle
authors.forename: Oscar G
authors.initials: OG
authors.lastname: Calderón
authors.forename: Cesar E
authors.initials: CE
authors.lastname: Caro
authors.forename: E
authors.initials: E
authors.lastname: Cabrera-Granado
authors.forename: M A
authors.initials: MA
authors.lastname: Antón
authors.forename: F
authors.initials: F
authors.lastname: Carreño