Tunable dual-band metamaterial absorber at deep-subwavelength scale

Abstract

A tunable dual-band metamaterial absorber composed of a gold square ring and a metal film separated by a strontium titanate dielectric is investigated. Two resonance peaks at frequencies 0.162 THz and 0.329 THz with over 99% absorbance are realized at room temperature. The maximum ratio between the lattice constant and the resonance wavelength is approximately 8.2%, which is much smaller than that of the formerly reported absorber. When the temperature changes from 150 K to 350 K, the two resonance absorption peaks at approximately 66.2% and 67.8% of the modulation depths are obtained. The effective impedance method and the LC equivalent circuit modelling are used to analyze the absorption mechanism of the proposed absorber. The proposed absorber is not affected by the change in polarization angles at normal incidence. The proposed structure adopts a single patterned square ring, which can be manufactured easily, and extended to other frequencies in applications such as biosensors, monitoring and imaging.