Optical-Resonance-Enhanced Photoemission from Nanostructured GaAs Photocathodes

A particular type of semiconductor photocathode with a nanostructured surface is shown to increase photoemission yield by more than a factor of three, compared to a flat photocathode. This improvement stems from the excitation of Mie resonances, which serve to reduce reflectivity and enhance light absorption near the surface, where electrons are more efficiently emitted. Nanostructured photocathodes, which can be described as ``electrically bright'' yet ``optically dark'', could benefit many applications, including high-current electron cooling of hadron beams in particle accelerators.