Epitaxially grown Yb:KLu(WO4)2 composites for continuous-wave and mode-locked lasers in the 1 μm spectral range

Epitaxial layers of up to 50% Yb-doped monoclinic KLu(WO4)2 could be successfully grown on passive KLu(WO4)2 substrates. These composite samples were characterized and continuous-wave and mode-locked laser operation was achieved with Ti:sapphire and diode-laser pumping. A 10% Yb-doped epitaxy provided an output power exceeding 500 mW at 1030 nm and a maximum slope efficiency of 66% with Ti:sapphire laser pumping. A 50% Yb-doped epitaxy exhibited serious thermal problems without special cooling and rather limited cw performance. Quasi-cw operation provided in this case an average output power of 43 mW at 1032 nm for a 10% duty cycle. More than 100 mW cw could be generated at 1030 nm also with diode-pumping of the 10% Yb-doped KLu(WO4)2 epitaxy. Pulses as short as 114 fs were generated at 1030 nm with this same sample under Ti:sapphire laser pumping in a laser mode-locked by a saturable absorber mirror.