Ultra-narrow-band terahertz perfect metamaterial absorber for refractive index sensing application

We numerically propose and demonstrate an ultra-narrow perfect metamaterial absorber (PMA) for refractive index sensing applications in the terahertz region. The designed PMA is only composed of a gallium arsenide (GaAs) cross-shaped resonator array on an opaque copper/silicon substrate. Simulated results show that the proposed PMA can achieve a near-perfect absorption peak with an absorptivity of 99.49% and a high quality factor value of 637 at 2.44THz. The physical mechanism of the narrow absorption is explained by the electric field, magnetic field and Poynting vector distributions. As a refractive index sensor, its sensitivity and figure of merit reach up to 1.94THz/refractive index unit (RIU) and 506RIU−1, respectively. These results make the proposed PMA to have great potential in detecting, imaging and sensing applications.