A polarization-insensitive triple-band perfect metamaterial absorber incorporating ZnSe for terahertz sensing

Abstract

In this work, a triple-band polarization-insensitive metamaterial structure with perfect absorption is proposed by incorporating a zinc selenide (ZnSe) spacer. The structure was optimally designed by varying the type of the spacer and the unit cell dimensions. The structure was simulated using the finite integration technique, and the results showed that the proposed design achieved a near-perfect absorption of about 99%, 99%, and 100% at 22.50, 28.98, and 35.14 THz, respectively. Its absorption characteristics were insensitive to the polarization angle and a wide range of incidence angles, making it an ideal absorber. Further investigations of the electric field, magnetic field, and surface current distributions were carried out to elaborate on the absorption characteristics at various resonance frequencies. The proposed device can also be used as a sensor that can detect the depth of the surrounding analyte and its refractive index. The device could detect the depth of the analyte with a peak sensitivity of 2.76 THz µm−1 and its refractive index with a peak sensitivity of 1.55 THz RIU−1. Thus, the design could have interesting terahertz applications.