Growth and spectral properties of Er3+/Yb3+-co-doped Ca3Ln2(BO3)4 (Ln=Gd, La) crystals

This paper reports the investigation of the growth and spectroscopic properties of Er3+/Yb3+-co-doped Ca3Gd2(BO3)4 and Ca3La2(BO3)4 crystals. Both crystals have been grown by the Czochralski method. The specific heats are 0.37 J/g/K and 0.45 J/g/K at 350 K for Er3+/Yb3+:Ca3Gd2(BO3)4 and Er3+/Yb3+:Ca3La2(BO3)4, respectively. They have a large absorption coefficient and broad full-width at half-maximum, which are 22 cm−1 and 7 nm for Er3+/Yb3+:Ca3Gd2(BO3)4 and 14.5 cm−1 and 9 nm for Er3+/Yb3+:Ca3La2(BO3)4, respectively. A strong emission band at 1450–1650 nm due to the 4I13/2→4I15/2 transitions in Er3+ was observed. The fluorescence lifetimes are about 590 and 650 μs for Er3+/Yb3+:Ca3Gd2(BO3)4 and Er3+/Yb3+:Ca3La2(BO3)4 crystals, respectively. The results show that when Yb3+ and Er3+ ions were co-doped into Ca3Gd2(BO3)4 and Ca3La2(BO3)4 crystals, Yb3+ as the sensitizer can enhance the absorption efficiency and lower the laser oscillations threshold of 1.5 μm Er3+ laser.