Optimizing Broadband Terahertz Modulation with Hybrid Graphene/Metasurface Structures

We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. ~This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission that arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also provides a new platform for possible nonlinear THz spectroscopy study of graphene.