Performance evaluation of metal photocathodes based on plasmonic nano-grating

Abstract

An important class of photocathodes is metal photocathodes, which are used in various systems due to their rapid response time. However, they have low quantum efficiencies due to electron scattering and high photon reflectance losses. Nanoscale surface engineering and plasmonic capability are used to improve the performance and increase the quantum efficiency of metal photocathodes. Plasmonic technology is a good choice due to optical trapping and increased electric field at the surface of the structure. In this study, metal photocathodes Au, Ag, Al, and Cu with similar nano-grating surfaces are designed and exposed to photon radiation and reflected spectra are analyzed and compared using FDTD method. In the reflectance spectrum, surface plasmon polaritons are excited at specific wavelengths and reduce the light reflection from metal nano-grating surfaces. The resonance wavelength adjustment is investigated by changing the height of the nano-grating grooves. The quantum efficiencies of metal photocathodes are calculated and compared with each other based on the relations and equations. The quantum efficiencies of nano-grating metal photocathodes relative to the flat surfaces show that the quantum efficiencies of gold, silver, copper, and aluminum nano-grating increase by 56-fold, 35-fold, 32-fold, and 14-fold, respectively, higher than their flat surfaces during resonant wavelengths.