Theoretical and numerical studies of dynamically tunable terahertz graphene-based chiral and anisotropic metamaterials

This thesis investigates how theoretical and numerical approaches can be used to design and analyse tunable terahertz graphene-based chiral and anisotropic metamaterials for applications in optoelectronics. Nine variations of metamaterials were designed and analysed to demonstrate the versatility of the technique: single-, dual-, and multi-function metamaterials working as a filter, multiband absorbers, broadband and multiband mirror, switch, inverter, a refractive index sensor, and a biosensor. Metamaterials were designed and optimized numerically in Computer Simulation Technology (CST) Software, while Equivalent circuit models (ECMs), parameter retrieval method, and Kramers–Kronig relations-based MATLAB codes were utilized in theoretical analysis.

The proposed metamaterial designs are dynamically tunable by varying bias voltage and they showed impressive component level performance in the THz frequency range (0.3–5.5 THz). The best designed metamaterials exhibit a maximum linear dichroism (LD) response of 100%, maximum absorption of 100%, with maximum four absorption/reflection bands, a maximum switching extinction ratio of 33.01 dB and a maximum circular dichroism (CD) response of 20%. From a sensing performance point of view, the maximum refractive index sensitivity was 0.96 THz/refractive index unit. With certain designs, the number and location of the absorption and reflection bands can be adjusted by rotating the incident electromagnetic field.

The obtained results demonstrated the significant potential of metamaterials in various research fields, their potential impact on the optoelectronics industry and the possibility of a proper design to make graphene-based THz metastructure fabrication more feasible.