We have developed a 5-µm optical parametric chirped pulse amplification (OPCPA) system delivering multi-GW femtosecond pulses at a 1 kHz repetition rate. The system is pumped by a highly stable 2-µm picosecond chirped pulse amplifier based on Ho:YLF gain media to exploit the high nonlinearity of ZnGeP₂ crystals for parametric amplification. In the 1 kHz pulse train, up to 1.3 mJ idler pulses were generated and compressed to 160 fs duration by dispersion management based only on bulk materials. The pulse energy represents the highest to date of any femtosecond mid-IR source beyond 4 µm. The OPCPA is characterized by an excellent stability with a pulse-to-pulse rms as low as 1.3%.

Adding a spatial light modulator in the setup pulse compression at 0.65 mJ pulse energy was performed. The resulting pulse duration of 75 fs corresponds to a sub-five-cycle signature and is close to the Fourier-limit. This pulse characteristics represents the highest peak power of 7.7 GW achieved for 5-µm OPCPA systems to the best of our knowledge, and, if focused to a 15-µm spot diameter, would reach a peak intensity of ~9 x 10¹⁵ W/cm².