A photoexcited switchable tristate terahertz metamaterial absorber

Abstract

In this study, we propose a photoexcited tristate terahertz metamaterial absorber which can switch between single-/single-/dual-band absorption modes in terahertz regime. The unit cell of the absorber incorporates two kinds of photosensitive semiconductor materials filled the gaps between four asymmetric right-angle wires and a cross wire. By applying different wavelengths of pump light on the absorber, two kinds of semiconductor materials can be excited to realize single-/single-/dual-band switchable absorption characteristics. The distributions of electric fields and surface currents at absorption peak frequencies under three absorption states are demonstrated to elucidate the switchable mechanism of the proposed absorber. Moreover, the absorption performance of the proposed tristate absorber is discussed under different polarization and incidence angles. The proposed structure is expected to be applied in the terahertz devices such as tunable absorbers, modulators, filters, and switches.