Temperature dependence of efficiency and thermal lensing of diode-laser-pumped Nd:YAG lasers

Efficiencies, lasing thresholds and thermal lensing of a Nd:YAG rod side-pumped with two 10 W diode-laser-arrays are measured for various rod temperatures between 80 K and 380 K. The threshold is reduced by a factor of 2.5–4 on cooling from room temperature to about 100 K, while the slope efficiency is increased by between 0% and 50% depending on the reflectivity of the outcoupling mirror. Extrapolation to a 240 W pumped laser gives an increase in optical efficiency of 25% to 30%. The thermal lensing measured with a beam deflection and an interferometric method is reduced by a factor of 10.