An ultrathin frequency dual-tunable Salisbury screen absorber based on graphene and strontium titanate in the terahertz region

Abstract

We present a frequency dual-tunable Salisbury screen absorber (SSA) based on graphene and strontium titanate (STO) in the terahertz region. Different from the classical SSAs, the absorber is composed of an optically thick layer of gold at bottom, a high-permittivity STO spacer and a single-layer nonstructural graphene film on top, which has the advantages of high absorption, lightweight, ultrathin thickness and frequency tuning. Simulation results show that the proposed SSA can obtain a strong Fabry–Perot resonance peak with 99.96% absorbance at 1.55 THz, whose performance is comparable with metamaterial-based perfect absorbers. When changing the STO temperature from 200 to 400 K, the resonance frequency shifts from 1.22 to 1.83 THz. As varying the graphene Fermi energy level from 0 to 1 eV, the resonance frequency shifts from 1.44 to 1.65 THz. Moreover, by changing the thickness of the STO spacer from 1.5 to 5.5μm, the resonance frequency can be passively tuned from 2.96 to 0.90 THz, achieving a larger frequency tuning range under small thickness variations. Meanwhile, this SSA exhibits excellent polarization insensitivity and maintains high absorption over 90% with varied incidence angle from 0° to 58° for both TE and TM waves. Such a design would have great potential applications in the fields of detecting, thermal emitting, and imaging.