Thin disk laser in the 2μm wavelength range

The thin disk laser is a successful concept for high output power and/or high pulse energy, high efficiency and good beam quality in the 1 μm range. Holmium-doped materials are a promising approach to transform this success to the 2 μm range. Ho:YAG is especially interesting for high pulse energies due to the long fluorescence lifetime (~ 8 ms) which provides good energy storage capabilities. We have realized a Ho:YAG thin-disk laser with a cw output power of 15 W at 2.09 μm and a maximum optical-to-optical efficiency of 37%. The laser was pumped with a Tm-fiber laser. Numerical simulations of the Ho:YAG thin disk laser show the potential for further scaling. As broadly tunable alternative, also a Cr:ZnSe thin disk laser was investigated. A Tm-fiber laser and a fiber coupled diode stack were tested as pump sources. A laser power of 3.5 W was achieved with diode pumping.