Measuring the Elevated Temperature Dependence of Up-Conversion in Nd:YAG

We present the measurement of the temperature dependence of the energy transfer up-conversion coefficient from the main upper laser level (⁴F_3/2) of 1at.% doped Nd:YAG. This is achieved by a very simple method employing a z-scan technique, monitoring the transmitted power of a probe laser tuned to the main absorption peak at 808 nm. For analysis, a simple model was developed and the temperature dependence of the absorption coefficient for this absorption band, covering the temperature range from 300-450 K, was measured. A spatially dependent two-level rate equation model is described, which simulates the relationship between the incident pump irradiance and the power transmitted by the crystal, as a function of its temperature. By comparing the experimental results with the model, we obtain a value for the energy transfer up-conversion coefficient of 4.7 ± 0.5 × 10^-17 cm³/s, at room temperature, decreasing to 1.6 ± 0.2 × 10^-17 cm³/s at 450 K.