Multipass cell post-compression schemes for high-quality ultrashot laser pulses

Abstract

[EN] This doctoral dissertation investigates the nonlinear post-compression of ultrashort laser pulses in multipass cells (MPCs), addressing a key challenge in ultrafast laser science: the generation of clean, few-cycle pulses from high-power Yb-based laser systems. As these lasers increasingly replace Ti:Sapphire systems in high-repetition-rate applications, efficient post-compression techniques become essential. A comprehensive numerical and theoretical framework was developed to simulate nonlinear propagation in MPCs, fully resolving the spatio-temporal and spatio-spectral dynamics (3+1)D, including diffraction, dispersion, and nonlinear effects. The framework enables systematic exploration and optimization of MPC performance under realistic experimental conditions. Through this approach, the thesis identifies the Enhanced Frequency Chirp Regime (EFCR) as an optimal operating regime for achieving broad spectra with high pulse cleanness in MPCs. The study extends to both gas-filled and bulk-filled MPCs, analyzing the influence of input chirp, mirror dispersion, and pulse distortions, confirming the intrinsic robustness of the MPC process. A grism-based compressor is designed and optimized using a particle-swarm algorithm to compensate complex spectral phases, yielding near-transform-limited pulses with excellent temporal cleanness. Altogether, the work provides a high-fidelity modeling tool and design strategy for next-generation ultrafast laser systems. Its insights and methods contribute directly to advancing stable, high-quality few-cycle pulse generation in Yb-based platforms and reducing experimental trial-and-error in post-compression design.