High fluorescence quantum efficiency of 1.8 μm emission in Tm-doped low silica calcium aluminate glass determined by thermal lens spectrometry

In this work, thermal lens spectrometry is performed to determine the fluorescence quantum efficiency (eta) of the F-3(4) level (1.8 mum emission) of 4 and 5 wt % Tm-doped water free low silica calcium aluminate glass. The eta value obtained for both high Tm contents was approximately 30%, which is in agreement with the Judd-Ofelt calculation. It is also verified that heat generation under 0.79 mum pumping, which presents a high quantum defect, is minimized by a cross-relaxation mechanism. The high eta values, and the excellent chemical and thermomechanical properties indicate this system is a potential host material for diode-pumped laser sources operating in the midinfrared spectral range. (C) 2004 American Institute of Physics.