Results of a detailed experimental investigation aimed at reducing the thermal loading problem in a cw Cr<sup>4+</sup>:forsterite laser at elevated temperatures are presented. From a Cr<sup>4+</sup>:forsterite crystal with a differential absorption coefficient of 0.57 cm<sup>−1</sup>, as much as 900 mW of cw output power has been obtained at 1.26 μm and at a crystal boundary temperature of 15 °C with an absorbed pump power of only 4.5 W at 1.06 μm. No chopping of the pump beam was necessary. An efficient radiative cooling technique was further employed to cool the laser and no subsequent power fading was observed. To the author’s knowledge, the measured absorbed power slope efficiency of 29.5% represents the highest cw power performance reported to date from a Cr<sup>4+</sup>:forsterite laser pumped by a Nd:YAG laser around room temperature. The role of the low differential absorption coefficient in the reduction of thermal loading is further elucidated by presenting comparative cw power performance data with a second Cr<sup>4+</sup>:forsterite crystal having a differential absorption coefficient of 1.78 cm<sup>−1</sup> in the temperature range between 12 and 35 °C. Finally, some interesting multipulse effects of the laser observed in the millisecond regime during quasi-cw operation at 50% duty cycle are described.
© 1998 Optical Society of America
(140.0140) Lasers and laser optics : Lasers and laser optics
(140.5680) Lasers and laser optics : Rare earth and transition metal solid-state lasers
(140.6810) Lasers and laser optics : Thermal effects
Alphan Sennaroglu, "Efficient Continuous-Wave Radiatively Cooled Cr4+:Forsterite Lasers at Room Temperature," Appl. Opt. 37, 1062-1067 (1998)