Multi-band absorber based on metal-silicon metasurface for sensing application

Based on the design featuring two rings and a cross on the surface, we propose a multi-band absorber utilizing a hybrid metal-silicon (Si) metasurface. This absorber is specifically designed to detect the refractive index of the surrounding environment. Through numerical simulation, we thoroughly investigated and analysed the performance of the absorber. The top layer of the structure consists of two rings that interact with the central cross, enabling multi-band resonance absorption. Our simulation results demonstrated the presence of four absorption peaks at frequencies of 2.3 THz, 3.79 THz, 5.79 THz, and 7.30 THz, with corresponding absorption efficiencies of 79.0%, 99.7%, 97.2% and 99.7%, respectively. Notably, the minimum Full Width at Half Maximum (FWHM) value is achieved only 0.13 THz. Therefore, our proposed multi-band metasurface absorber exhibits significant potential for sensor applications.