Graphene-based polarization-insensitive metamaterials with perfect absorption for terahertz biosensing applications: Analytical approach

In this paper, a terahertz metamaterials absorber structure with an average sensitivity of 2.538 THz/RIU is developed, which is very useful in various industries, including chemical and environmental industries. The structure was simulated using the finite integration technique. The transmission line theory was presented with the help of a transmission matrix, impedance matrix, and scattering matrix to analyze this structure and the relations between input impedance and reflection coefficient were expanded with the help of those matrices. The proposed structure consists of four layers from top to bottom as follows: Graphene/polysilicon/SiO2/Au. This structure has an excellent absorption of 99.99 % at 7.628 THz. The suggested design has a high Q-factor of 23.4. This structure is incident wave polarization insensitive and also has broad bandwidth from the angle of impact. This structure can then be used as a sensor in the terahertz band with different refractive indices. In addition, the electric field distribution of the proposed structure is shown to observe the physical mechanism of the structure at various resonance frequencies. In addition, the equivalent circuit diagram has been presented for a better understanding of the working principle of the proposed structure. Simulation and computational results show that this structure can detect blood glucose, malaria mosquito bites, and early detection of cancer.