Molecular Free Electron Vortices in Photoionization by Polarization-Tailored Ultrashort Laser Pulses

Carrier-envelope-phase and helicity control of electron vortices and spirals in photodetachment

Formation of electron vortices and spirals in photodetachment from the H^- anion driven by isolated ultrashort laser pulses of circular polarization or by pairs of such pulses (of either co-rotating or counter-rotating polarizations) are analyzed under the scope of the strong-field approximation. It is demonstrated that the carrier-envelope phase (CEP) and helicity of each individual pulse can be used to actively manipulate and control the vortical and spiral patterns in the probability amplitude of photodetachment. Specifically, we show that the vortical patterns can be rotated in momentum space by the CEP of the driving pulse (or, of two identical pulses); thus, offering a tool of pulse characterization. For co-rotating pulses of arbitrary CEPs, a novel type of structured vortices is discovered. Also, we demonstrate that the momentum spirals are formed when photodetachment is driven by two pulses of time-reversal symmetry, which is accompanied by absolute disappearance of vortical structures. Hence, we attribute the spiral formation to annihilation of vortices with antivortices, which are generated by time-reversed pulses comprising the train. Finally, the CEP and helicity control of spiral structures is demonstrated, leading to their rotation in momentum space.