Liquid-nitrogen-cooled Ti:Al2O3 laser

At 93 K, sapphire (Al₂O₃) has much better thermal properties than at room temperature. By taking advantage of the improved thermal properties, a Ti:Al₂O₃ laser was operated with 350 W of output power under thermal steady-state conditions. Model calculations of thermal lensing and higher order thermooptic aberrations indicate that the output power capability is 200 times larger at 77 K than at 300 K, consistent with experimental results. The discussion includes consideration of optical aberrations present in the laser and their effect on laser operation, a theoretical calculation of the onset of thermal steady state, and an examination of nonthermal issues. It is concluded that high-power operation of liquid-nitrogen-cooled Ti:Al₂O₃ lasers up to 1 kW is possible using a rod geometry