Laser performances and spectroscopic investigation of Yb:LuAG grown by µ-PD technique

In the present work we report on the laser emission and spectroscopic investigation of a LuAG:Yb3+crystal, grown by micro-pulling down technique. In our knowledge the performances of the laser here reported are the best obtained for this grown technique. LuAG melts congruently around 2350 K and it has a cubic crystal structure [1], isomorphs to the most popular YAG. The relevance of this host relay on the almost constant thermal conductivity with the doping level, in contrast with the decreasing one of YAG. This feature makes LuAG an appealing material for high power laser applications opening the way to obtain low cost laser grade old and new materials. Low-power laser experiments in CW regime were performed in order to assess the crystal quality, employing several different output couplers in the range 0–30% in an X shaped cavity. The pump diode was a single-mode 300-mW laser diode (FLC GmbH), emitting at 935 nm with a narrow single-longitudinal and single-spatial mode with 50-pm linewidth. The Yb:LuAG laser crystal was a 4.5-mm long, 1%-doped rod, with a diameter of 3 mm. The active medium was contacted to a metallic plate, without any active cooling, and oriented at the Brewster angle in order to minimize insertion losses. The measured lifetime of the 2F5/2 manifold as 1030±20 µs at room temperature and the absorption coefficient was about 1.1 cm−1 at the pump wavelength.