Femtosecond Yb-fiber laser synchronously pumped HgGa_2S_4 optical parametric oscillator tunable in the 4.4- to 12-μm range

摘要

We employed an HgGa_2S_4 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 M~2 < 1.1. No crystal damage was observed at average pump intensities as high as 60 kW/cm~2.