115-W TM-YAG DIODE-PUMPED SOLID-STATE LASER

A compact diode-pumped Tm:YAG laser capable of generating greater than 100 W of CW power at 2 mu m has been demonstrated, a scalable diode e nd-pumping architecture is used in which 805-nm radiation, coupled to the wing of the Tm3+ H-3(6)-H-3(4) absorption feature, is delivered to the end of the laser rod via a lens duct, To facilitate thermal manag ement, 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 leng th, the lower doping level results in higher power, indicating that cr oss relaxation is still efficient while offering lower thermal stress and reduced absorption at the laser wavelength, Output powers for vari ous output coupler reflectivities are compared to the predictions of a quasi-three-level model, Thermal lensing, cavity stability, and stres s-induced birefringence measurements are described, The beam quality w as analyzed with the 2% Tm-doped rod and a hat output coupler, yieldin g M-2 values of 14-23.