Ultra-broadband terahertz absorber based on graphene ribbons

Terahertz (THz) absorbers have been verified to be a promising candidate for the biosensing and imaging modern devices. In this paper, an ultra-broadband THz absorber based on periodic arrays of graphene ribbons (PAGRs) is presented. The recently proposed analytical circuit model of PAGRs besides a developed transmission line theory is used to describe the absorber structure as circuit elements. Using circuit theory and impedance matching concept, the input impedance of the structure is adjusted to be closely matched to the free space in a wide frequency range. As a result, the bandwidth of 90% absorption extended up to 100% of central frequency. The results show that the Full-wave simulations (while using Finite Element Method) and circuit model approach verify each other. The proposed structure and its performance can be a useful structure and be utilized in filters and sensors.