Evaluation of spectroscopic properties of Yb3+-doped glasses

The absorption and emission properties of numerous glasses doped with Yb3+ ions have been investigated. The emission cross sections have been evaluated using the measured absorption spectra and principle of reciprocity, and again using the Fuchtbauer-Ladenburg formula. Agreement between the two methods is typically within 25% for most materials. The spectroscopic properties of the F-2(7/2)-F-2(5/2) transition have been found to be very sensitive to the Yb3+ site environment as well as an hypersensitive transition, and their values increase as the asymmetry of the Yb3+ site becomes higher. High asymmetry of the Yb3+ site is essentially caused not only by large difference in the cationic field strengths between network formers around the [YbO6] coordination sphere, but also by difference in the coordination numbers of oxygens surrounding network formers that are associated with the Yb3+ through the oxygens. A system of Yb:(15-25)P2O5-(10-20)Nb2O5-(0-15)B2O3-(48-55)RO (R=Mg, Ca, Sr, Ba, and Zn) glasses which possess higher asymmetry of Yb3+ ligands has been developed. These glasses exhibit the most useful laser properties, and are expected to be substantially superior to Yb:SiO2 and Yb:ZBLAN glass fiber lasers in many key spectroscopic parameter values.