Quantum Efficiency Enhancement by Mie Resonance from GaAs Photocathodes Structured with Surface Nanopillar Arrays

TL;DR

This paper demonstrates that GaAs nanopillar array Mie resonators significantly enhance quantum efficiency by reducing reflectivity and increasing optical density, leading to a 3.5-fold improvement in photoemission performance for photocathodes.

Contribution

It introduces a novel GaAs nanopillar array NEA photocathode with Mie resonances that improve light absorption and electron emission, surpassing traditional GaAs photocathodes.

Findings

Reflectivity reduced to less than 6% at visible wavelengths

Quantum efficiency increased by 3.5 times

Enhanced electron emission area and optical density

Abstract

A new type of negative electron affinity (NEA) photocathode based on GaAs nanopillar array (NPA) Mie-type resonators was demonstrated for the first time. For visible wavelengths, the Mie resonances in GaAs NPA reduced light reflectivity to less than 6 percent compared to a typical value great then 35 percent. Other benefits of NPA resonators include an enhanced density of optical states due to increased light concentration and increased electron emission area. These features resulted in improved photoemission performance at the resonance wavelength demonstrating maximum quantum efficiency 3.5 times greater than a GaAs wafer photocathode without the NPA structure. This optically dark photocathode (sub-percentage light reflectance over visible wavelengths) but possessing electrically high-brightness (enhanced electron emission) provides new opportunities for practical applications such as large-scale electron accelerators, high-resolution night-vision imaging and low energy electron microscopy.