Figure 4.

Optical modulation of free electrons. (a) Energy comb of electron losses and gains produced by ultrafast interaction with evanescent light fields in the PINEM approach: experiment⁷⁷ and theory⁸⁷ comparison. Adapted with permission from ref (87). Copyright 2010 American Chemical Society. (b) Laser-amplitude dependence of the electron energy comb produced by PINEM interaction, revealing quantum billiard dynamics among different electron energy channels separated by the photon energy ℏω. Adapted with permission from ref (88). Copyright 2015 Springer-Nature. (c, d) Tilt-angle dependence of the PINEM energy comb produced by using a planar film (c) and associated transfers of lateral linear momentum (d). Adapted with permission from ref (83). Copyright 2018 Springer-Nature. (e) PINEM in the intermediate-coupling regime showing a (n + 1)/n loss–gain intensity ratio in the EELS spectra of silver nanoparticles with 100 keV electrons under ns-laser illumination, superimposed on regular spontaneous EELS features, for beam positions as shown in the color-coordinated spots of the upper-left image, along with gain and loss energy-filtered images in the upper-middle and -right plots. Adapted with permission from ref (81). Copyright 2019 Elsevier B.V. (f) Intense-coupling regime resulting in a large number of PINEM energy sidebands under total-internal-reflection phase-matched illumination (i.e., with the electron velocity matching the surface-projected light speed inside the glass). Adapted with permission from ref (89). Copyright 2020 Springer-Nature. (g) Transfer of angular momentum between light and electrons, as revealed in a configuration similar to (c) through a donut shape of the electron intensity in the Fourier plane after PINEM interaction. Adapted with permission from ref (90). Copyright 2019 Springer-Nature. (h) Electron modulation into a train of attosecond pulses upon propagation from the PINEM interaction region over a sufficiently large distance to interlace different energy sideband components in an electron microscope. Adapted with permission from ref (91). Copyright 2017 Springer-Nature. (i, j) Single electron pulses produced by streaking a train of pulses following the scheme shown in panel (i) and experimental demonstration based on the observation of the time-resolved electron current in a table-top e-beamline setup (j). Adapted with permission from ref (92). Copyright 2020 American Physical Society.