Generation of supercontinuum compressible to single-cycle pulse widths in an ionizing gas

Analysis of the evolution of submillijoule few-cycle light pulses in an ionizing gas reveals physical mechanisms and scenarios enabling the generation of high-intensity supercontinuum radiation compressible to singlecycle pulse widths. The main properties of supercontinuum generation in this regime are analyzed by numerically solving a spatiotemporal evolution equation for a few-cycle light field adapted to include ultrafast ionization phenomena in a gas medium. The enhancement of ionization-induced phase shifts and shockwave effects, which is inherent in few-cycle fields, is shown to be the key factor for a substantial intensification of the high-frequency wing of the spectrum, giving rise to broadband radiation with appropriate spectral phase profiles that can be compressed to single-cycle pulses upon an accurate temporal and spatial chirp compensation. The dynamics of few-cycle light fields in an ionizing gas is shown to be sensitive to the initial pulse width, pulse shape and ionization regime. 3 Author to whom any correspondence should be addressed. New Journal of Physics 10 (2008) 093001 1367-2630/08/093001+19$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft