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Coherent superposition of electronic states induces attosecond electron motion in molecules. We theoretically investigate the strong-field ionization of this superposition state by numerically solving the time-dependent Schrödinger equation. In the obtained photoelectron momentum distribution, an intriguing bifurcation structure appears in the strong-field holographic interference pattern. We demonstrate that this bifurcation structure directly provides complete information about the status of the transient wave function of the superposition state: the horizontal location of the bifurcation in the momentum distribution reveals the relative phase of the involved components of the superposition state and the vertical position indicates the relative coefficient. Thus, this bifurcation structure takes a snapshot of the transient electron wave packet of the superposition state and provides an intuitive way to monitor electron motion in molecules. [ABSTRACT FROM AUTHOR]

Nonlinear metasurfaces provide a promising platform for integrated nonlinear photonic devices owing to their unprecedented capability of nonlinear wavefront manipulation. However, the previously reported second‐harmonic (SH) metasurfaces are mainly based on the nonlinear Pancharatnam–Berry phase modulation. While this method is quite convenient and robust, it shows limitations of modulation efficiency and the difficulty in extending to multidimensional combined modulations. Here, the resonant nonlinear synthetic metasurface is proposed and experimentally demonstrated for independent phase and amplitude modulations of the SH beam. A high SH modulation efficiency of 75% (with a theoretical limit of 90%) is achieved in the polarization‐dependent SH metalens. Moreover, SH holographic imaging with phase and amplitude (at 2 and 4 levels) combined modulation is realized experimentally. Compared with the pure‐phase modulation, the signal‐to‐noise ratios are increased by 2 and 3 times when 2‐ and 4‐level amplitude controls are introduced. This is not only an important step in the improvement and innovation of holographic display technology, but also paves a distinct avenue toward multifunctional, higher efficiency, and ultracompact nonlinear optical devices. [ABSTRACT FROM AUTHOR]

By numerically solving the two-dimensional time-dependent Schrödinger equation, we investigate the strong-field photoelectron holography (SFPH) for different atomic and molecular targets. The results show that the photoelectron hologram is capable of providing structural information-the phase of scattering amplitude. In our calculations, the holographic pattern shifts with the target, indicating the phase difference between various targets. However, for the near-forward scattering, the phases of scattering amplitude for different targets are similar and thus no structural information has been retrieved in the previous works on near-forward scattering hologram. We suggest to use the backward scattering photoelectron hologram to extract this type of structural information. This paves a significant step towards time-resolved imaging of molecular structure and dynamics with the concept of SFPH. [ABSTRACT FROM AUTHOR]