Electrically tunable solid-state terahertz metamaterial absorbers

This work presents the design of electrically tunable solid-state metamaterial absorbers in the terahertz spectrum. The proposed devices consist of a metal-insulator-metal resonant cavity formed between a subwavelength metal stripe grating and a back metal reflector. The dielectric spacing between the metallic parts is occupied by a deeply subwavelength layer of n-doped GaAs. By reverse biasing the Schottky junction formed at the interface between GaAs and the top metal grating, the thickness of the associated carrier depletion zone is controlled and, hence, the GaAs complex permittivity profile in the resonant cavities. Optimized structures are derived based on the mechanism of critical coupling, achieving amplitude modulation of the reflected terahertz wave with low insertion losses and theoretically infinite extinction ratio.