Design of a Hybrid Enhanced Photocathode Based on Plasmonic Nano-Grating

The most important and effective part of any light detector is the photocathode. In this research, in order to improve the efficiency of the photocathode optical response, the plasmonic phenomenon is used and a new photocathode is designed and simulated based on the finite difference time domain (FDTD) method. By designing a periodic nano-grating on the surface, a structure is presented that makes it possible to couple the incoming light to an electron density wave on the surface. Plasmonic resonance is created in the desired wavelength range and the field strength is greatly increased. In this way, the metal-semiconductor becomes an excellent absorber. For this purpose, photocathodes with planar and non-planar (nano- grating) structures consisting of GaAs and Au are simulated separately. Then, the plasmonic nano- grating structure consisting of Au-GaAs composite materials is simulated and compared with the plasmonic nano- grating structure of gold, so that the absorption rate of the structure is increased by 16.1%. The plasmonic nano- grating structure consisting of Au-GaAs in the visible spectrum shows better performance in increasing the photocathode efficiency due to higher absorption. The structure provided for the photocathode has the advantage of filtering the incoming light with excellent accuracy and quality. Another important feature is the creation of multiple resonant frequencies simultaneously with the formation of repetitive geometry.