Actively tunable broadband terahertz absorption using periodically square-patterned graphene

We propose an actively tunable broadband perfect absorber using a square-patterned graphene-spacer-polysilicon-spacer-metal structure. The simulated results show that the absorber can reach nearly perfect broadband terahertz absorption with over 99.5% (90%) absorbance from 1.52 (1.27) to 2.23 (2.51) THz, corresponding to the normalized bandwidth of 37.5% (65.6%) under normal incidence with the graphene Fermi level of 0.7 eV. The absorption spectra show a clear independence of the polarization and the angle of incidence. By adjusting the graphene Fermi level from 0 to 0.7eV, the peak absorbance can be continuously tuned from 15 to 100% without shifting the absorption frequency band. (C) 2018 The Japan Society of Applied Physics