Reflection-mode nanostructured GaAlAs photocathode with narrow-band response to 532 nm

The underwater photoelectric detection equipment mainly uses 532 nm laser as the light source, but the corresponding photocathodes like Na2KSbCs, GaAs and GaAsP have a wide spectral response region and are easily affected by other signals. Thereby, GaAlAs are materials worth developing because of their adjustable band gap, which usually is used as a window layer of GaAs-based photocathode. In this paper, the finite difference time domain (FDTD) method is used to carry out nanostructure design simulations. The results show that GaAlAs with Al component of 0.63 can obtain the cutoff wavelength near 532 nm, which is an excellent photocathode material to meet the requirement of narrow-band spectral response of 532 nm laser. Furthermore, the light absorptance can be improved effectively by the quadrangular prism or cylinder nanostructured array prepared on the Ga0.37Al0.63As emission layer surface, and the maximum light absorptance can reach 96.2% at 532 nm for the cylinder nanostructure array with a height of 900 nm and a base width of 100 nm. Nevertheless, the reflection-mode Ga0.37Al0.63As photocathode with the quadrangular prism nanostructured array can be slightly influenced with incident angle of light.