  The transformation of electromagnetic energy into matter represents a
fascinating prediction of relativistic quantum electrodynamics that is
paradigmatically exemplified by the creation of electron-positron pairs out of
light. However, this phenomenon has a very low probability, so positron sources
rely instead on beta decay, which demands elaborate monochromatization and
trapping schemes to achieve high-quality beams. Here, we propose to use
intense, strongly confined optical near fields supported by a nanostructured
material in combination with high-energy photons to create electron-positron
pairs. Specifically, we show that the interaction between near-threshold
gamma-rays and polaritons yields higher pair-production cross sections, largely
exceeding those associated with free-space photons. Our work opens an
unexplored avenue toward generating tunable pulsed positrons at the
intersection between particle physics and nanophotonics.

Optics;Other Condensed Matter