Electrically Tunable Perfect Terahertz Absorber Based on a Graphene Salisbury Screen Hybrid Metasurface

Graphene, as a popular 2D semiconductor, with a carrier concentration that can be extensively tailored by external stimulants, such as electric bias and photoexcitation, is a promising candidate for active optoelectronics. An electrically tunable perfect terahertz absorber is presented by integrating a metallic grating into classical graphene Salisbury screen. The measurement shows that perfect absorption can be achieved for even lightly-doped graphene and a modulation depth up to 25% is realized. Numerical simulation and analytical model based on the transmission line theory are developed to validate the design, showing a good agreement with the measured results. In addition, dependence of the terahertz response on physical dimensions and polarization of the incident terahertz field is also experimentally explored. It indicates that the hybrid terahertz device is able to function as tunable perfect absorber or tunable polarizer with an extinction ratio up to 23 dB. These results demonstrate the feasibility of using low carrier mobility chemical vapor deposition (CVD) grown graphene for tunable perfect terahertz absorption, which is suitable for potential applications, such as terahertz switching, and time domain and spatial domain modulation.