Fluorescence quantum efficiency of Er3+ in low silica calcium aluminate glasses determined by mode-mismatched thermal lens spectrometry

The fluorescence quantum efficiency of Er3+ in low silica calcium aluminate glasses, with nominal composition 58 CaO, 27.1 − x Al2O3, 6.9 MgO, 8 SiO2, x Er2O3, 0.1 ⩽ x ⩽ 1.5 (mol%), melted in air and under vacuum, has been measured using the mode-mismatched thermal lens spectrometry, with excitation beam wavelength at 488 nm and 804 nm. From 0.1 up to 1.1 mol% of Er2O3 the quantum efficiency is around 0.65 for vacuum-melted samples, and around 0.46 for air-melted ones. The quenching of the quantum efficiency appears above 1.3 mol% of Er2O3. The thermal diffusivity was also obtained, with results showing a decrease from 5.69 × 10−3 cm2/s (undoped sample) to 4.78 × 10−3 cm2/s (for the highest doped sample, 1.5 mol% of Er2O3).