Phase-Matching Water Window Attosecond Pulses with Sub-cycle Waveforms

Abstract

Water window attosecond pulses are generated in He gas using sub-cycle tailored fields delivered by a parametric waveform synthesizer. High-harmonic spectra and photon flux measurements are carried out with two driving field intensities. Signatures of transient phase matching are identified by observing a strong modulation of the energy cutoff when the relative phase among the synthesizer's constituent pulses approaches zero