Cooling schemes for longitudinally diode laser-pumped Nd:YAG rods

Longitudinal diode laser pumping causes pronounced inhomogeneous heating of the laser material. The effect of the thermal load on the mechanical and optical properties is significantly influenced by the method used for cooling the pumped surface. Four methods for longitudinally pumped Nd:YAG rods were compared experimentally and with finite-element (FE) analysis. The pumped surface exposed to air or to flowing water, a sapphire plate pressed onto the pumped surface and composite rods, having an undoped pumped end, were investigated. The comparison includes temperature and stress distributions with the emphasis on thermal lensing. Careful validation of the FE code with experiments allowed to numerically comparing the cooling methods under identical conditions.