Effect of plasmonic near field on the emittance of plasmon-enhanced photocathode

The surface plasmon polaritons make the emittance of the electron beam emitted from the photocathode complicated. In this article, numerical investigations are carried out to study the influence of the plasmonic near field (PNF) excited by a square hole array on the beam emittance. The characteristics of the emittance induced by PNF are studied. The coupling between the emittance caused by PNF and the original intrinsic emittance due to the excess energy of electrons and the surface roughness of the cathode is discussed. The results provide insights into the suppression of the emittance caused by PNF and new possibilities to break the limits of the nature of the materials, improving the performance of a photocathode.