Few-cycle pulses with 40 W average power at 100 kHz from a flat-top pumped OPCPA

Optical parametric chirped pulse amplification (OPCPA) has become a standard technique to amplify ultrashort pulses with high average power over a broad spectral range, from the visible to the mid-infrared regions of the electromagnetic spectrum. In this work, a high average power OPCPA delivering few-cycle pulses around 800 nm at a repetition rate of 100 kHz is introduced. The system is characterized by a novel and simple scheme to generate a flat-top pump beam that allows for efficient pump-to-signal energy transfer with minimum spatio-temporal distortions at 40 W output average power (0.4 mJ per pulse). A maximum output power of 60 W is also demonstrated, albeit with lower pulse quality.