Periodically extended architecture for power scaling of diode-pumped solid-state lasers: proof of concept with Pr:LiYF4.

We report on a power-scaling concept for blue diode-pumped visible lasers based on a periodically extended multi-crystal cavity architecture. This design is validated using a continuous-wave praseodymium laser employing three 0.5 at.% Pr:LiYF4 crystals, delivering 7.14 W of output power at 639.7 nm (in the red) with a slope efficiency of 30.8% (relative to the incident pump power). The laser exhibits linear polarization (σ) and near-diffraction-limited beam quality (M2x,y < 1.15) at an incident pump power of 25.2 W provided by six 444 nm free space GaN laser diodes. We demonstrate the linear scaling of total cavity losses and an almost constant optical conversion efficiency with the number of laser crystals. The design criteria for periodically extended laser cavities are formulated based on resonator stability conditions and mode-matching efficiency, considering multiple thermal lenses. The proposed architecture can be applied to high-power laser operation on different transitions, as well as to laser amplifiers.