High-Fidelity Few-Cycle Laser Pulses Generated Via Nonlinear Ellipse Rotation

Ultra-high peak-power laser systems, such as those commissioned by the ELI-ALPS European laser facility, require seed pulses with ultra-broadband spectra and high temporal contrast, which can be generated via nonlinear optical techniques, such as the widely used cross-polarized wage (XPW) generation [1]. Alternatively, Nonlinear ellipse rotation (NER) can also be used for nonlinear pulse cleaning [2]. Indeed, the intensity-dependent rotation of the polarization ellipse of an intense pulse undergoing nonlinear propagation implies that polarization discrimination can be implemented to separate the high-intensity peak from the unwanted low-intensity pedestal of the pulse. NER in noble-gas-filled hollow waveguides is particularly attractive as it can be combined with SPM-induced spectral broadening to achieve even shorter pulse duration [3,4].