Dielectric stereostructure on graphene for ultrawideband terahertz absorber

A high-performance ultrawideband terahertz absorber is proposed. Constituted by silicon hemi-ellipsoid and monolayer graphene that is separated by a dielectric spacer from a bottom metal reflector. The absorber achieved an ultrawide absorption bandwidth from 2 THz to more than 10 THz with an average absorbance of 95.72%, and the relative bandwidth is 133%. The excellent absorption properties are owing to the presence of graphene and the shape morphing of the silicon hemi-ellipsoid, in which multiple discrete graphene plasmon resonances and continuous multimode Fabry-Perot resonances can be excited. By coupling the graphene plasmon resonances and Fabry-Perot resonances, the absorption spectrum is extended and smoothed to realize an ultrawideband absorber. The incident angular tolerance can reach 60 degrees. The results will shed light on the better performance of terahertz trapping, imaging, communication, and detection.