Coherent perfect absorber with independently tunable frequency based on multilayer graphene

We propose two terahertz coherent perfect graphene-based absorbers that can simultaneously realize the tunable resonant frequency and absorption. The Fermi energy of graphene, which can be changed by applied electric fields affect the frequency of absorption peaks. By adjusting the phase difference between two interfering beams, the absorption intensity can be controlled. The simulated results indicate that the absorptivity can achieve nearly 100% change and the adjusting range of absorption frequency is up to 16 THz. With the flexible movement of four absorption peaks, the absorption bandwidth over 90% can be extended to 10 THz. What is more, this paper displays the application to photoswitch by phase modulation. In particular, the proposed absorbers are polarization-insensitive and almost omnidirectional. We hope that our results can provide substantial help for the potential applications in the future metamaterial devices.