Absorbed Pump Power, Thermal Profile and Stresses in a cw Pumped Nd:YAG Crystal.

A Nd : YAG crystal 7.6 cm long and 6.35 mm in diameter was pumped by two krypton filled arc lamps in a double elliptical pumping cavity. The pump radiation absorbed and the heat dissipated by the Nd : YAG crystal were measured. This was done by a calorimetric measurement of the heat removed from the YAG crystal cooling loop and by monitoring the laser output power. In separate experiments the pump cavity transfer efficiency and the optical losses of the resonator were determined. The results of these measurements show that in the case of a high powered YAG system having an output power of 250 W at 12 kW input, which is six times threshold, 7.5% of the electrical input to the lamp is being absorbed by the crystal, and 40% of the absorbed pump power leaves the crystal as stimulated emission. The experiments revealed that 15% of the electrical input into the krypton arc lamps is emitted into the absorption bands of Nd:YAG crystal. The temperature profile and the associated stress components in the YAG crystal are calculated from the experimental data.