Novel field assisted photocathodes with nanoscale grating antennas

A field-assisted photocathode is the only existing one that has high sensitivity at the wavelength beyond 1100nm. The photomultiplier tubes (PMTs) with the field-assisted photocathode have been widely used for the low light level detection in a near infrared region. These have been used, for example, as high sensitivity, fast response detectors for time resolved photoluminescence measurement of semiconductors and the measurement of singlet oxygen emission from living organism. However, the higher dark currents are the substantial disadvantage for the field-assisted photocathodes. Recently, we reported on the field-assisted photocathode with surface plasmon antennas in order to reduce the dark currents. In this presentation, we present the spectral response characteristics of the field-assisted photocathodes with the nanoscale grating antennas fabricated on the surface in order to guide the incident photon fluxes into the nanoscale apertures of the photocathode by the surface plasmon resonance. In addition, the comparisons of the spectral response characteristics between the calculations and the experimental results are demonstrated. The results show the nanoscale grating antennas serve to guide the incident photon fluxes into the nanoscale apertures of the photocathodes. The results also exhibit the nanoscale metallic antennas would be utilized to realize a photocathode with extremely low dark current especially in the near infrared region.