Optical Properties of Chromium and Erbium Co-Doped Alumina-Germania-Calcia-Yttria-Silica Based Fiber

We report the fabrication details and optical characterization of novel Erbium (Er) and Chromium (Cr) co-doped alumina-germania-calcia-yttria-silica fiber. Co-doping with Er and Cr is chosen as potentially promising for enhancing the fiber's fluorescent and amplifying potential in the near-infrared (NIR) region at 'resonant' (viz. into Er band absorption maximum, @976 nm) and 'non-resonant' (viz. off Er band while into Cr broad absorption band, @905/1064 nm) excitations. Our results reveal strong coupling, at both kinds of excitation, of Er- and Cr- subsystems in the fiber. This effect is justified by the presence of pronounced 1.5-1.6 mu m emission, characteristic to Er ions, at 905/1064 nm excitations and, at 976-nm excitation, by notable spectral broadening of the fiber's NIR fluorescence and gain, comprising the lines inherent to Er3+ (1.5-1.6 mu m) and Cr3+/Cr4+ (1.15-1.45 mu m), as compared to purely Er-doped silicate fiber, exemplified here by commercial 'L20' (Er20-4/125) and 'L40' (Er40-4/125) fibers.