Multipass-cell-based pulse compression to sub-two-cycle duration at 2 µm

We present a laser source at 1.9 µm wavelength delivering 11.0 fs pulses with 1.36 mJ pulse energy and 137 W average power at a repetition rate of 101 kHz, achieved by applying pulse compression in a gas-filled multipass cell to a Tm:fiber chirped-pulse amplification (Tm:fCPA) system. This work marks the first, to the best of our knowledge, demonstration of MPC-based sub-two-cycle pulse compression in the shortwave infrared (SWIR) region and sets a new benchmark for the highest average power reported from a sub-two-cycle SWIR source. The exceptional combination of high pulse energy and average power makes this source well-suited for driving nonlinear frequency conversion processes across a broad spectral range, including terahertz, mid-infrared, and soft X-ray.