Quantum control and characterization of ultrafast ionization with orthogonal two-color laser pulses

We study ultrafast ionization dynamics using orthogonally polarized two-color (OTC) laser pulses involving the resonant “first plus second” (ω + 2ω) scheme. The scheme is illustrated by numerical simulations of the time-dependent Schrödinger equation and recording the photoelectron momentum distribution. On the basis of the simulations of this resonant ionization, we identify signatures of the dynamic Autler-Townes effect and dynamic interference, in which their characterization is not possible in the spectral domain. Taking advantage of the OTC scheme we show that these dynamical effects, which occur at the same time scale, can be characterized in momentum space by controlling the spatial quantum interference. In particular, we show that with the use of this control scheme, one can tailor the properties of the control pulse to lead to enhancement of the ionization rate through the Autler-Townes effect without affecting the dynamic interference. This enhancement is shown to result from constructive interferences between partial photoelectron waves having opposite-parity, and found to manifest by symmetry-breaking of the momentum distribution. The scenario is investigated for a prototype of a hydrogen atom and is broadly applicable to other systems. Our findings may have applications for photoelectron interferometers to control the electron dynamics in time and space, and for accurate temporal characterization of attosecond pulses