Fabry-Perot resonance cavity for ultra-thin GaAs negative electron affinity photocathodes

Electron accelerator and photodetector require negative electron affinity photocathode (NEA-PC) with high quantum efficiency (<i>QE</i>), short response time and low mean transverse energy (<i>MTE</i>). Finding a NEA-PC that simultaneously meets all these requirements is challenging. Here, a Fabry-Perot (F-P) cavity with a high reflective silver (Ag) mirror was used for GaAs NEA-PC, which was analyzed by a coupled Monte Carlo opto-electronic model. For the concerned wavelengths of 532 and 780 nm, enhanced light absorption peaks with <i>Q</i>-<i>factor</i> > 20 were obtained in a 100 nm ultra-thin GaAs NEA-PC layer by the standing wave resonance of the F-P cavity, which lead to the enhanced <i>QE</i> higher than that of the normal thick ones, the picoseconds short response time, and the <i>MTE</i> less than 70 meV, respectively. Given these properties, Ag F-P resonant ultra-thin GaAs NEA-PC represent a promising photocathode to provide the high-brightness short-pulse electron beams and high-sensitive fast-response detectors for the electron accelerator and photodetection applications, respectively.