Photoluminescence Characteristics of Bi(m+)-Doped Silica Optical Fiber: Structural Model and Theoretical Analysis

The energy levels associated with structural models of different valence states of Bi ions in Bi-doped silica optical fiber are investigated using the density functional theory of quantum-chemical calculation. The Bi 5+ , Bi 3+ , and Bi + local structure models with and without Al ion are analyzed and compared with respect to their fluorescence characteristics. The result reveals that the special fluorescence effect possibly comes from Bi 5+ and/or Bi 3+ ions. Bi 5+ ions may combine with Al ions that activate the luminescence center of Bi 5+ ions. Furthermore, the distinctive fluorescence bands are efficiently generated by the coupling effect between Bi 5+ and Al 3+ ions. The fluorescence of Bi 3+ ions may come from the Bi 3+ ions with Al-free ion. Fluorescence of Bi + ions may exist, but its contribution to the fluorescence is nominal.