Photoexcited terahertz metamaterial absorber with tunable broad absorption band

A few photoexcited terahertz (THz) metamaterial absorbers (MAs) with tunable narrow bands have been reported and there is still a lack of photoexcited THz MAs with tunable broad absorption bands. In this paper, we present a photoexcited THz MA with a tunable broad absorption band. The presented MA is composed of a layer of high-permittivity resonators, a layer of photoconductive silicon, a PDMS (polydimethylsiloxane) layer and a ground gold layer. With the increasing conductivity of photoconductive silicon, the proposed MA achieves a tunable broad absorption band. When the conductivity is 1.5 x 104 S/m, the proposed MA achieves the absorptivity of exceeding 90% over the broad frequency range of 1.48-2.73 THz and the maximum bandwidth is up to 1.25 THz. In addition, the proposed MA is insensitive to polarization and exhibits stable absorption performance within 45 degrees. This work may provide a feasible reference to design photoexcited THz MA with a tunable broad absorption band.