Spectroscopic study of optical centers formed in Bi-, Pb-, Sb-, Sn-, Te-, and In-doped germanate glasses.

We have shown that the broadband near-IR (NIR) fluorescence recently discovered in Bi-doped glasses is not specific due solely to Bi ions. Glasses doped with different 6p (Bi, Pb) and 5p (Sn, Sb) ions exhibit very similar behavior characterized by four major spectral peaks observed in two-dimensional excitation-emission plots and the lifetime of metastable level of about 400 micros. Our results challenge the existing models of optical centers in Bi-doped glasses. Point defect optical centers caused by the presence of 6p (Bi, Pb) and 5p (Sn, Sb) ions are proposed for the explanation of NIR emission in these laser materials.