Mid-infrared optical parametric amplification pumped with a low-conversion fiber four-wave mixing source.

We demonstrate an optimized cascaded χ(3)-χ(2) source for picosecond mid-infrared pulse generation at 3.34 µm. A 1064 nm Yb-fiber master oscillator power amplifier system pumps a photonic crystal fiber (PCF) to generate a weak Stokes seed at 1.56 µm via four-wave mixing (FWM), which, together with residual pump light, pumps and seeds optical parametric amplification (OPA) in an MgO-doped PPLN crystal. We empirically maximize the OPA idler conversion efficiency by performing a systematic cutback of the PCF to optimize the Stokes seed power relative to the residual pump power. The optimum PCF length of 0.15 m has only 0.03% FWM Stokes conversion and generates 98 mW of idler power (196 nJ pulse energy) at 3.34 µm, with a conversion efficiency of 9.8%. These results show that low-conversion FWM provides an effective self-synchronized seed for compact fiber-pumped mid-infrared parametric sources.