Three-dimensional photoelectron holography with trichromatic polarization-tailored laser pulses

Abstract

We present a three-dimensional (3D) photoelectron wave packet holography scheme based on polarization-tailored trichromatic femtosecond laser pulses for the determination of quantum phases in atomic multiphoton ionization (MPI). Experimentally, we combine supercontinuum polarization pulse shaping with photoelectron tomography for the reconstruction of the 3D photoelectron momentum distribution (PMD). To demonstrate the 3D photoelectron holography scheme, we superimpose a sculptured wave packet encoding a relative continuum phase with a reference wave packet. In particular, we create a sculptured angular momentum superposition wave packet by (2+1) resonance-enhanced MPI of potassium atoms using a counter-rotating circularly polarized bichromatic pulse sequence. The sculptured wave packet, consisting of states with different orbital angular momentum quantum numbers, interferes with the reference wave packet generated by direct 3-photon ionization with a circularly polarized pulse of the third color. Depending on the circularity of the reference pulse, interference of both wave packets gives rise to 3D photoelectron holograms with c 2 or c 4 rotational symmetry in the laser polarization plane, i.e., in the azimuthal direction. In the polar direction, the azimuthal interference pattern undergoes a phase-shift revealing the relative quantum phase between the p- and f-type continuum partial waves in the sculptured wave packet. We determine the relative continuum phase by fitting the parameters of an analytical model of the hologram to the measured 3D PMD and confirm the result by direct extraction of the continuum phase difference from the polar-angle-dependent azimuthal phase-shift of the photoelectron angular distribution.

Multichromatic supercontinuum polarization shaping applied to photoelectron holography

“…Now, the LCP reference pulse creates an |f, 3⟩-type reference wave packet. Because the magnetic quantum number difference is 4 in this case, the resulting hologram is c 4 -symmetric [82]. A distinct advantage of the trichromatic schemes over the single-color schemes is based on the energetic disentanglement of the relevant MPI pathways from other frequency-mixing pathways and also the single-color pathways.…”

“…The labels 'probe' and 'reference' indicate that the structured wave packet is a photoelectron hologram. In our second and third scenario (see sections 4.2 and 4.3), we utilize the holographic properties of the superposition wave packet to determine the spectral phase of the partial wave packets and infer details of the MPI dynamics [43,82].…”

“…Switching the circularity of the red pump pulse to RCP, as shown in (b), creates a superposition of continuum states with different orbital angular momentum, specifically, the |f, −1⟩-and the |p, −1⟩-type continuum. The angular part of the probe wave packet is hence described by |f, −1⟩ + a p (ε) |p, −1⟩, where the generally energy-dependent complex-valued parameter a p (ε) accounts for the different ionization amplitudes and phases of the two continua [41,82]. Recently, we demonstrated the retrieval of the phase of a p by photoelectron holography [82].…”

“…The angular part of the probe wave packet is hence described by |f, −1⟩ + a p (ε) |p, −1⟩, where the generally energy-dependent complex-valued parameter a p (ε) accounts for the different ionization amplitudes and phases of the two continua [41,82]. Recently, we demonstrated the retrieval of the phase of a p by photoelectron holography [82]. The difference between the magnetic quantum numbers of the interfering partial wave packets is 2 in this case, yielding the c 2 -symmetric hologram shown in figure 2(b).…”

“…(1) We introduce a shaper-based photoelectron tomography technique to reconstruct the three-dimensional (3D) photoelectron momentum distribution (PMD). In contrast to the established photoelectron tomography technique [80,81], where a half wave plate (HWP) is used to rotate the entire laser field, we use optical phases to rotate the hologram [82] and compare the results of both techniques. (2) We utilize the hologram for the time-resolved and phase-sensitive investigation of ultrafast photoionization dynamics in the bound atomic system.…”