Abstract

The recent discovery of near infrared (NIR) photoluminescence (PL) of bismuth-doped silica glasses [1] led to the development of a new class of laser media that provides broad gain in 1100-1250nm range [2]. However, the luminescent centre (or centres) is not clearly identified up to now and this point is actively discussed in the literature. Different authors tentatively assigned this NIR PL to the electronic transitions of Bi⁵⁺ [1], [(AlO_4/2)⁻,Bi⁺] complexes, Bi⁺, Bi²⁺, clusters of Bi atoms, BiO molecules and, recently, to negatively charged [Bi₂]⁻² pairs dispersed in glass host [3]. In our recent report we have demonstrated experimentally that at least clusters of Bi atoms should be eliminated from the list of potential candidates [4]. In the present communication we give experimental evidence that the NIR PL observed in bismuth-doped silica glasses should be connected to the electronic transitions from triplet excited states (ES) in contradiction to what was suggested in [3].

© 2009 IEEE