Real-time fine-tuning ultrafast supercontinuum generation and nonlinear pulse compression in hybrid multipass cell

The self-compression of near-IR laser pulses in a multipass cell requires anomalously dispersive mirrors to balance the dispersion within the cell, which limits the setup flexibility and energy scaling. To address this limitation, we explore the feasibility of employing both solid and gas within multipass cells, thereby eliminating the need for chirped mirrors. In this hybrid multipass cell, we utilize a KDP plate as the nonlinear material to broaden the spectrum, leveraging its anomalous dispersion properties. Then, the cell is filled with normally dispersive gases to dynamically adjust the net dispersion throughout the process. This combination enables real-time fine-tuning of dispersion and precise control over the compression process. Based on our comprehensive carrier-resolved 2D+1 propagation simulations, despite pulse splitting during evolution, a strong isolated pulse can be achieved at the final stage when cavity parameters - such as gas pressure and number of passes - are properly optimized. Our results demonstrate that the proposed hybrid multipass cell can achieve spectral broadening and temporal compression by factors of 14 and 21, respectively, resulting in a few-cycle pulse duration of 4.6 fs with more than 40% energy efficiency. This method offers a significant improvement over traditional self-compression techniques, providing a cost-effective and adjustable alternative for near-IR pulse compression.