Speaker
Description
Research on nanostructure and metamaterial fabrication benefits from microscopy techniques that enable imaging of electromagnetic near-fields with nanometer-scale resolution. Photon-induced near-field electron microscopy (PINEM) measures the effect of the Lorentz force component aligned with the electron propagation direction through changes in the electron energy spectrum, thereby quantifying net acceleration or deceleration [1]. It has previously been shown that pre-modulating the electron beam into an attosecond pulse train enables phase-resolved measurements of the integrated longitudinal Lorentz force [2,3].
In earlier work, we demonstrated that transverse Lorentz force components can be probed using 4D STEM, where transverse momentum transfer causes a broadening of the electron distribution on a pixelated detector that is proportional to the force magnitude [4, 5]. However, this method does not directly provide phase information.
Here, we introduce pre-shaping of the electron beam through the longitudinal Kapitza–Dirac effect, generating attosecond bunches in the electron probability density prior to the interaction. This structured beam probes the optical near-field and experiences transverse deflections that depend on the instantaneous phase of the transverse Lorentz force. By analyzing the phase-dependent modulation of the detected electron distribution, both the amplitude and phase of the transverse near-field components can be reconstructed. Because the transverse Lorentz force components are linked to spatial gradients of the longitudinal field, this method also provides complementary access to information about the complete electromagnetic near-field.
References
[1] B. Barwick, D. J. Flannigan, and A. H. Zewail, Nature 462, 902 (2009).
[2] D. Nabben et al., Nature 619, 63 (2023).
[3] J. H. Gaida et al., Nat. Photonics 18, 509 (2024).
[4] P. Koutenský et al., ACS Photonics 12, 4452 (2025).
[5] P. Koutenský et al., arXiv:2604.20463, (2026).