Excited-state absorption cross sections in the 800-nm band for Er-doped, Al/P-silica fibers: Measurements and amplifier modeling

Excited-state absorption (ESA) cross sections were determined for the 800-nm band of Er-doped, Al/P-silica fibers. The oscillator strength of the ESA transition exceeds that of the 800 nm, ground-state absorption (GSA) transition by a factor of approximately= 2.3, in reasonable agreement with a Judd-Ofelt calculation. The extended, long-wavelength tail of the GSA band leads to a region around 820 nm where the GSA cross section approximately= ESA cross section. The cross sections were incorporated into an amplifier model for pumping in the 800-nm band. Codirectional and the bidirectional pumping schemes were analyzed for excitation near the peak and in the long wavelength tail of the GSA band. Pumping in the tail for either pumping scheme or pumping near the peak for the bidirectional scheme are predicted to produce a significant improvement in the small-signal gain.<>