Ho3+ doped fluorophosphate glasses sensitized by Yb3+ for efficient 2 μm laser applications

In this paper, new Ho3+/Yb3+ co-doped fluorophosphate glasses with superior thermal stability against crystallization have been synthesized. Intense 2 μm emissions have been observed when pumped by a conventional 980 nm laser diode. High infrared transmittance (82%) and low hydroxyl concentration (16.7 ppm) can be realized according to the analysis of infrared transmittance spectrum. Based on the measured absorption spectra, a thorough calculation of the Judd-Ofelt parameters and radiative properties has been carried out. The predicted spontaneous transition probability, emission cross section and gain coefficient of Ho3+:5I7→5I8 can reach to 74.11 s−1, 4.53×10−21 cm2, and 0.8 cm−1, respectively. Besides, the energy transfer coefficients from Yb3+ to Ho3+ have also been calculated and discussed. The results suggest the prepared glass is a good candidate for efficient 2 μm laser.