We report proof-of-concept experiments generating 5.5W of rapidly tuneable 589nm laser radiation through SHG of
1178nm radiation generated by optical parametric amplification in Lithium Triborate. The two stage OPA was pumped
by a frequency doubled mode-locked Nd:YVO<sub>4</sub> laser (15ps, 1.5MHz, 50W) and seeded by a tuneable diode laser,
allowing convenient tuning on and off the Na D2 line. Our findings imply that if scaled up in power and with modified
pump pulse duration, this approach can lead to a versatile high-power Na guide star source which can be built from
readily available commercial components.
High average power (10-50W) slow mode-locked lasers operating with repetition rates of a few MHz provide a unique combination of high peak power, short pulse duration, and high brightness that makes them ideal for applications in pulsed laser ablation and nonlinear optics. With peak powers in the MW range and near diffraction-limited output beams, focussed intensities can exceed 10<sup>12</sup>W/cm<sup>2</sup>: sufficient for ablation of most solid materials or to saturate nonlinear optical interactions.