LAUSR

Abstract. We employed an HgGa2S4 nonlinear crystal to achieve the highest average power from a high-repetition rate mid-infrared femtosecond optical parametric oscillator (OPO), synchronously pumped near 1 μm. The continuous tuning of the nonresonated idler extended from below 4.4 to beyond 12 μm. The OPO was pumped by a 6.5-W, 1.035-μm, 81-MHz, 220-fs Yb-fiber laser. The idler output reached an average power of over 355 mW at 5.2 μm (at a signal power of > 2 W at 1.25 μm). The peak quantum efficiency of the OPO approached 40%. The signal output was diffraction limited with M2 < 1.1. No crystal damage was observed at average pump intensities as high as 60 kW/cm2.