Led by professor Liu Yunquan and professor Gong Qihuang, the research team from School of Physics, Peking University, have recently experimentally measured the laser-intensity-dependent photoelectron momentum distributions (PMDs) of Ar atoms with two-color (ω+2ω) corotating circularly polarized fields. Entitled “Universal Description of the Attoclock with Two-Color Corotating Circular Fields”, the progress has been published on Physical Review Letters.
The interference patterns on PMDs reveal complex structures with respect to the laser intensity ratio. The main above-threshold ionization peaks and sidebands on PMD distribute oppositely when the fundamental field is much weaker than the second-harmonic field, and the PMD reveals a characteristic single-lobe distribution when the two colors have comparable intensities. Using strong-field approximation, they analytically explain how the interference pattern on PMD evolves with respect to the relative laser intensity. By analyzing the interference pattern, they reveal the phase difference and the temporal evolution of the emitting electron wave packets.
This work show that, when monitoring the intensity ratio, the double-pointer attoclock geometry with corotating circular fields can be universally mimicked as the spatially rotating temporal double-slit experiments with the variable slit width, which can be used to probe and control strong-field ionization. [Peipei Ge, Meng Han, Yongkai Deng, Qihuang Gong, and Yunquan Liu, “Universal Description of the Attoclock with Two-Color Corotating Circular Fields”,Phys. Rev. Lett. 122, 013201(2019)