Fiber-laser-based, high-repetition-rate, picosecond ultraviolet source tunable across 329-348 nm

We report a compact, fiber-laser-based, high-repetition-rate picosecond source for the ultraviolet (UV), providing multi-tens of milliwatt of average power across 329-348 nm. The source is based on internal sum-frequency-generation (SFG) in a singly-resonant optical parametric oscillator (OPO), synchronously pumped at 532 nm by the second harmonic of a picosecond Yb-fiber laser at 80 MHz repetition rate. Using a 30-mm-long single-grating MgO:sPPLT crystal for the OPO and a 5-mm-long BiB3O6 crystal for intracavity SFG, we have generated up to 115 mW of average UV power at 339.9 nm, with >50 mW over 73% of the tuning range for 1.6 W of input pump power. The UV output exhibits passive rms power stability of ~2.9% rms over 1 min and 6.5% rms over 2 hours, in high beam quality. Angular acceptance bandwidth and cavity length detuning with pump power and crystal temperature have also been studied. Peer Reviewed