Growth and spectroscopic properties of Yb–Ho co-doped CNGG crystal

Abstract Yb and Ho co-doped gallium calcium niobium garnet (Yb–Ho:CNGG) crystal was successfully grown for the first time by the Czochralski method, and its spectroscopic properties were systematically studied. Based on the J-O theory the intensity parameters were calculated to be Ω2 = 2.8518 × 10−20 cm2, Ω4 = 2.3457 × 10−20 cm2 and Ω6 = 0.7577 × 10−20 cm2, respectively. What's more, the oscillator strengths, fluorescence branching ratios and lifetime were also evaluated. The gain cross-sections around 2 μm were calculated with different population inversion. The lifetime of Ho3+:5I7 was measured to be 6.41 ms and the long upper lever of the energy transition of 5I7→5I8 demonstrated that the Yb–Ho:CNGG is suitable for the oscillation of 2 μm laser.