Experimental and numerical demonstration of driver pulse spectral width and phase dependence in near-single-cycle pulse post-compression generation

For many years, light-matter interaction in the strong-field regime has benefited from continuous improvement of femtosecond lasers, in terms of peak power or repetition rate. One of the most current major challenges is the achievement of high-energy, near single-cycle pulses. Such performances are of primary interest in attosecond science for producing intense isolated bursts of extreme ultraviolet light through high-harmonic generation in gases or solids. We present here a detailed experimental and numerical study on a helium filled hollow-core fiber-based post-compression stage. Our measurements highlight the importance of the width and phase of the input spectrum on the spectral broadening, and on the resulting post-compressed pulse. Near Fourier-transform-limited pulses as short as 3.5 fs, carrying a 2.5 mJ energy centered at 750 nm at 1 kHz repetition rate, and leading to a compression factor greater than seven, are demonstrated. The numerical results are in good agreement with the experimental data. Here, spectral broadening is governed by the Kerr effect and the self-steepening on the trailing edge of the guided pulse.