Amplification of few-cycle pulses at 21 µm using a hybrid BBO-based OPCPA scheme

Simple and compact laser systems facilitate the stable and reproducible generation of high-power few-cycle laser pulses. We demonstrate the amplification of 15 fs pulses at 2.1 µm, employing a hybrid phase-matching scheme for optical parametric chirped pulse amplification. A combination of two BBO crystals with type-I and type-II phase-matching placed in close vicinity is utilized as a single amplification stage. This allows for a greatly simplified layout, achieving high conversion efficiency while avoiding the backconversion regime and the associated spatiotemporal distortions. The resulting system yields mJ-level pulses with integrated electro-optic sampling to directly measure the output waveform and study ultrafast light–matter interaction.