Work performed toward satisfying Objective 1:
We have designed, fabricated, and characterized EDPHSs that in interaction with electron beams, generate photons with tailored properties. Particularly using concepts from photon sieves, metamaterials, and holography, the directionality, duration, carrier wavelength, polarization, angular momentum, and the intensity of the generated light pulses have been controlled, as demonstrated in a number of publications by us (Fig. 1)(Nanophotonics 9 (15), 4381-4406 (2020); Nano Letters 20 (8), 5975-5981 (2020); Nature communications 10 (1), 1-8 (2019)).
We have examined as well various mechanisms of radiation from the electron beams, covering the transition radiation, plasmon-induced radiation, as well as exciton-enhanced CL radiation (Communications Materials 2 (1), 1-11 (2021); arXiv:2101.01465; arXiv:2103.14442 (accepted in ACS Applied Nanomaterials); arXiv:2101.11516). Excitons particularly can lead to more photon yield compared to plasmonic lattices, though the far-field coherence is not as pronounced as for plasmonic materials. Hence as a second step, we aim at hybrid materials structures enabling higher photon yields and spatio-temporal coherent features.
Work performed toward satisfying Objective 2:
Interaction of electron beams with light and nanostructures lead to both elastic and inelastic processes. The so-called Kapitza-Dirac effect (KDE) is a prominent example of a two-photon process that lead to electron diffraction by a standing-wave pattern of light. In contrast with the KDE, PINEM is predominantly an inelastic process, that happens due to the interaction of electron beams with near-field distributions, hence momentum criterion for single-photon processes can be easily satisfied. Both processes though, are generally modelled using an Eikonal approximation known as Volkov states or nonrecoil approximation, that constitutes the electron-beam phase modulations caused by the electromagnetic interactions. We have recently developed a numerical Maxwell-Schrödinger toolbox that allows for exploring the dynamics of electron and light interactions beyond adiabatic approximations.
Recently, we have predicted and explored by means of our numerical experimentations, conditions for quantum-path interferences between both single and two photon process, that are achieved by including two inclined light beams of certain intensity and wavelengths (New Journal of Physics 21 (9), 093016 (2019)). Our methods paves the way towards novel kinds of boson-sampling devices that exploit matter waves, though yet to be explored.
In addition, we have simulated the recoil that the electron receives when interacting with laser-induced photonic modes of nanostructures (Fig. 2) (Physical Review Letters 125, 080401 (2020)). Particularly we showed that when the electron wave packet strongly interact with near-field photons, a prominent KDE effect is observed that allows for exploring dynamics by observing the diffraction patterns rather than detecting the spectrum.
Most recently, we exploited the interaction of spin-polarized two-electron wave packets with laser-induced plasmon oscillations, with the aim to understand the role of exchange correlations in transferring the phase information among electron-orbital constituents.
