Inband-pumped, broadband bleaching of absorption and refractive index changes in erbium-doped fiber

Broad-band absorption bleaching in erbium-doped fiber by in-band narrow-linewidth pumping is reported. For the first time, spectra of absorption bleaching of erbium-doped fiber is measured and the refractive index changes inferred through the Kramers–Kronig relations in this true two-level system in order to understand its operation in the external cavity of a laser.