High-sensitivity tunable perfect absorber in Dirac semimetal-buffer-substrate

We demonstrate the numerical feasibility of achieving a highly sensitive tunable perfect absorber by inserting a thin buffer layer between a disk-shaped bulk Dirac semimetal (BDS) and a substrate. Our findings indicate that the insertion of a thin buffer film directly beneath the BDS disk enhances absorption intensity, resulting in perfect absorption. Conversely, without a buffer film, the same structure does not exhibit such improved absorption properties. Moreover, the absorption peaks in the proposed device can be effectively controlled and tuned by altering physical parameters such as the permittivity and thickness of the buffer layer, operation frequency, and the Fermi energy level of the BDS disk. Importantly, our proposed structure exhibits high refractive index sensitivity (S=17.74 (mu m)/RIU) and a remarkable figure of merit (FOM=20.22) compared to previous works. These results demonstrate the potential of the proposed structure for use in optical devices across various fields, including terahertz sensors.