Speaker
Description
We introduce free electrons as powerful tools for probing deep-subwavelength structures of light known as superoscillatory electromagnetic fields. Their sub-nanometer spatial resolution allows free electrons to overcome the fundamental limitations of conventional optical-field characterization techniques. By exploiting the electron interaction with optical near fields, we theoretically demonstrate access to superoscillatory features in both propagating and evanescent optical waves. As an example, plasmonic moiré superlattices generate arrays of nanoscale superoscillatory structures that feature extreme sensitivity to external perturbations. Mapping these structures provides a powerful route for detecting and reconstructing variations in the underlying optical near field. In addition, the interaction imprints deep-subwavelength modulations onto free-electron wave functions, enabling structured electron beams beyond the diffraction scale. Our results establish free electrons as a uniquely powerful probe of nanoscale optical phenomena and open exciting opportunities in nanophotonics, plasmonics, and electron-wave engineering.