Abstract
In the present study, a broad negative refractive index (NRI) performance is achieved in the terahertz frequency range (0.6{0.9 THz) through the design of multi-layered fishnet metamaterial (FMM). Herein, the conventional fishnet structure is modified by smoothing the sharp corners to reduce the electric field concentration and improve NRI. At corner radius, r = 30 μm, an effective refractive index of — 11:14 is achieved with lower electric field concentration at the corners. A multilayer structure of up to 40 layers is studied to achieve a broad NRI frequency response. The frequency band of NRI response is improved from 0.034 THz for a single layer structure to 0.178 THz for 28 layer structure, almost 6 times the original bandwidth. With the increase in the number of layers, the improvement in NRI and Figure of Merit (FOM) is observed, and maximum NRI and FOM values of— 87:5 and 12.67 are achieved at 28 layers. This multilayer broadband design can surpass tunable response of available electro-optic materials. With an optimal combination of NRI and FOM, the presented multilayer approach can achieve a low-loss, broadband performance.