Thermal lens study of energy transfer in Yb3+/Tm3+-co-doped glasses

Energy transfer ( ET) and heat generation processes in Yb3+/Tm3+-co-doped low-silica calcium-aluminosilicate glasses were investigated using thermal lens and photoluminescence measurements. Stepwise ET processes from Yb3+ to Tm3+, with excitation at 0.976 mu m, produced efficient emission in the mid-infrared range at around 1.8 mu m, with high fluorescence quantum efficiency (similar to 0.50) and relatively low thermal loading (<= 0.42). An equation was deduced for the description of the thermal lens results which provided the absolute value of the ET efficiency and optimal Tm3+ concentration that result in population of the 1.8 mu m Tm3+ emitting level. These results suggest that the studied co-doped system would be a promising candidate for the construction of high-power diode-pumped solid-state lasers in the mid-infrared range, which are especially important for the purpose of medical procedures. (C) 2007 Optical Society of America.