The tuned absorptance in multilayer graphene-dielectric structures by intraband transition

In this work, using the transfer-matrix method, the optical transport process is investigated, with graphene inserted into multilayer dielectric structures, theoretically and numerically in the THz regime. When the incident frequency is lower than the graphene Fermi energy, the optical intra-band transitions provide the main contribution to the graphene surface current. The absorptance can be enhanced to about 50% with only one graphene/dielectric layer in air. When increasing the number of dielectric layers coated with graphene, the absorption increases. Periodic absorption peaks are observed in multilayer structures. The positions of the absorption peaks as a function of the frequency and the incident angle are in accordance with the positions of the abrupt change in the reflection coefficient phase and of the imaginary solution of the Bloch wavevector in expanding periodic structures using Bloch theorem.