IR Bismuth active centers in optical fibers: Combined   excitation-emission spectroscopy
  3D excitation-emission luminescence spectra of Bi-doped optical fibers of various compositions were measured in a wide wavelength range 450-1700 nm. Such luminescence spectra were obtained for Bi-doped pure silica and germania fibers, and for Bi-doped Al- or P-codoped silica fibers (at room and liquid nitrogen temperatures). The energy level schemes of IR bismuth active centers in pure silica and germania core fibers were derived from spectra obtained. The energy level schemes similarity of bismuth active centers in these two types of fibers was revealed. 
S. V. Firstov, V. F. Khopin, I. A. Bufetov, E. G. Firstova, A. N.   Guryanov, E. M. Dianov
physics.optics