10-µJ few-cycle 12-µm source based on difference-frequency generation driven by a 1-kHz mid-wave infrared OPCPA

We report on high-energy, few-cycle pulse generation in the long-wave infrared spectral region via difference-frequency generation (DFG) in GaSe and AgGaSe₂ nonlinear crystals. The DFG is driven by the signal at 3.5 µm and idler at 5 µm of a high-power mid-wave infrared optical parametric chirped pulse amplification (OPCPA) system operating at a 1-kHz repetition rate. The DFG pulses contain up to 17 µJ of energy and cover a spectrum from 8.5 µm to 14.5 µm. They are generated with a conversion efficiency of 2.1 %. Compression results in 10.2-μJ pulses with sub-150-fs duration, corresponding to less than four optical cycles.