Absorption-enhanced nanopillar-arrayed Na₂KSb photocathode for improving image intensifier performance

Na₂KSb photocathodes utilized in image intensifiers typically comprise flat films with a thickness of 0.15 µm, to balance optical absorption depth and minority-carrier (electron) diffusion length. However, these configurations often exhibit insufficient light absorption across visible and near-infrared wavelengths, resulting in low quantum efficiency. To address this challenge, we developed a nanopillar-arrayed Na₂KSb photocathode integrated with a bilayer TiO₂ two-dimensional nanograting. This design preserved the standard thickness while achieving a 30.1% enhancement in optical absorption through guided-mode resonance and transmission diffraction. Consequently, the measured quantum efficiency increased by 3.75% at 0.68 µm. Our study provides insights for improving absorption efficiency in nanopillar-arrayed Na₂KSb photocathodes, thereby enhancing the performance of image intensifiers.