Attosecond X-ray pulse generation by waveform control of mid-infrared laser

We perform detailed macroscopic simulations of high harmonic generation in a He gas cell by combining a few-cycle, carrier-envelope-phase-stabilized 4-<i>µ</i>m driving laser pulse with a single-cycle, 400-nm pulse, demonstrating that the two-color laser configuration significantly boosts harmonic generation efficiency in the 1.05-1.25 keV photon-energy range compared to a single-color scheme. Additionally, we show that isolated keV attosecond pulses can be successfully produced through the combined approach of phase matching and two-color waveform control.