Effect of erbium concentration on spectroscopic properties and 2.79 μm laser performance of Er:CaF2 crystals

The effect of erbium concentration on spectroscopic properties of Er:CaF2 crystals was investigated. Two highest absorption cross-sections (sigma(abs)) at 967 nm were achieved in the 4at.% and 8at.% Er:CaF2 samples with the value of 0.22 x 10(-20) cm(2) and 0.23 x 10. 20 cm(2), respectively. And the 4at.% and 8at.% Er:CaF2 samples also had the highest emission cross-section (sigma(em)) at 2727 nm with the value about 0.67 x 10(-20) cm(2). Lifetime of I-4(13/2) decreased faster than that of I-4(11/2) with the increase of erbium concentration. Under laser diode (LD) pumping, the continuous-wave (CW) laser operations around 2.79 mu m were demonstrated in the 4at.%, 8at.% and 11at.% Er:CaF2 samples. And the 4at.% Er:CaF2 sample had the best laser performance with a maximum output power of 0.282 W and a slop efficiency of 13.9%. (C) 2016 Optical Society of America