Influence of electron-wave-packet amplitude and phase modulations on photoelectron angular distributions in strong-field ionization

We theoretically investigate strong-field ionization driven by counterrotating two-color laser fields, focusing on the interplay between the amplitude and phase of electron wave packets (EWPs) in shaping photoelectron angular distributions. Using the strong-field approximation (SFA), we disentangle the respective contributions of EWP amplitude and phase and identify an abrupt angular shift of the sideband (SB) peak between the second and third orders in short-range potential systems. This phenomenon originates from a transition in dominance between amplitude and phase modulations, highlighting a significant role of the EWP amplitude that has been largely overlooked in previous studies. Furthermore, we incorporate long-range Coulomb effects using a Coulomb-corrected SFA model and demonstrate that the Coulomb potential amplifies and shifts the phase contribution, inducing notable angular shifts in SB structures. Our results uncover a previously underappreciated impact of amplitude modulation on strong-field photoelectron dynamics.