Multi-mode graphene based terahertz amplitude modulation enhanced by hollow cross H-structured metasurface

A graphene-metasurface based terahertz (THz) amplitude modulator enhanced with the hollow cross H array in a metal film is proposed. Based on the transmission line theory, the equivalent analysis model of the modulator is built. With the model, the multi-mode resonation excited by the metasurface is analyzed and the amplitude modulations of the THz transmission are discussed. By applying modulation voltage between the metallic metasurface and graphene film in the experiment, three enhanced modes in the transmission spectrum are observed and the maximum modulation depth is enhanced to 49.3% in the band of 0.1–1.8 THz. The experimental results exhibit a good agreement with the theory analysis. (paper)