Triple-Mode Switchable Terahertz Metamaterial Absorber with Tunable Absorption Characteristics

Abstract

Dynamically tunable terahertz metamaterial absorbers integrating with active materials have been widely explored. However, there are still problems that need to be urgently solved, such as modulation depth deficiency, a lack of multiparameter-tunable characteristics, and so on. In this paper, a multiparameter-tunable terahertz absorber composed of two concentric double-opening resonant rings is proposed. Semiconductor silicon and germanium are introduced to fill the openings, so that the absorber possesses three different absorption modes. Regulating semiconductor conductivities using different pump lasers allows dynamic switching among the three absorption modes to be realized. Adjusting the polarization angle of incident THz waves through device rotation facilitates easy and convenient modulation of the absorption amplitude. Calculation results show that the maximum modulation range for amplitude is 0 to 90.1%. Thus, due to the existence of two regulatory degrees of freedom, absorption mode switching and amplitude modulation are realized simultaneously. Most importantly, continuous modulation of the absorption amplitude is obtained at every resonant point in all three absorption modes without frequency drift. This scheme provides a new perspective for exploring future terahertz absorbers.