Multistage optical parametric amplifier for the generation of sodium guide star

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:YVO4 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.