Generate short isolated attosecond pulses with waveform-shaped infrared laser by controlling a trajectory parameter

Reaching ever shorter duration of isolated attosecond pulses (IAPs) is an ongoing mission in attosecond science. Widely usage of long-wavelength driving lasers has greatly broadened bandwidths for generating IAPs. We propose a strategy to further exploit the ability of a long-wavelength laser in producing short IAPs. We discovered a scaling relationship between IAP duration and a trajectory parameter that is associated with the classical cutoff trajectory of high-order harmonic generation (HHG) in gases. This trajectory parameter can then be used to generate short IAPs by shaping laser waveform. We demonstrate the effectiveness of our methods with numerical calculations of HHG from Ne. Our results show that using an additional short-wavelength (e.g., deep ultraviolet) laser pulse together with the infrared is an effective way to shorten IAP duration (from 76 to 47 as in our example), for which insightful physical explanations are provided.