115-W Tm:YAG diode-pumped solid-state laser

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Abstract
A compact diode-pumped Tm:YAG laser capable of generating greater than 100 W of CW power at 2 /spl mu/m has been demonstrated. A scalable diode end-pumping architecture is used in which 805-nm radiation, coupled to the wing of the Tm/sup 3+3/H/sub 6/-/sup 3/H/sub 4/ absorption feature, is delivered to the end of the laser rod via a lens duct. To facilitate thermal management, undoped YAG end caps are diffusion bonded to the central doped portion of the laser rod. For 2% and 4% Tm-doped rods of the same length, the lower doping level results in higher power, indicating that cross relaxation is still efficient while offering lower thermal stress and reduced absorption at the laser wavelength. Output powers for various output coupler reflectivities are compared to the predictions of a quasi-three-level model. Thermal lensing, cavity stability, and stress-induced birefringence measurements are described. The beam quality was analyzed with the 2% Tm-doped rod and a flat output coupler, yielding M/sup 2/ values of 14-23.