Abstract:
In this paper, a tunable absorber structure based on a graphene hexagonal array in the terahertz range is investigated. The graphene hexagonal absorber is simulated by the finite element method. The effects of the geometry, graphene Fermi energy level and incident light angle, and light polarization on the absorptance of the structure are investigated. The results show that the absorptance spectrum of the proposed absorber is tuned from 6.1 THz to 9.1 THz when the Fermi energy increases from 0.4eV to 0.9eV. The absorptance peak shifts to lower and higher frequencies with increasing hexagonal side length and Fermi energy level, respectively. The absorption of the structure is over 90% in the incident light angle range from 0 to 80º for the TE polarization and in the range of 0-40º for the TM polarization. Also, results indicate that the absorption peaks shift to the lower energies with increasing the dielectric constant of the dielectric layer.  Manuscript profile

In this present paper, the linear optical absorption coefficient in an array of quantum wires under the external electric and magnetic fields is studied. The effects of the external fields and structural parameters such as wires' radius, the number of wires, the distance between wires, and the Al composition on the optical absorption are investigated. Results indicate that the resonant peak of the absorption coefficient shifts toward the lower photon energies with increasing structural parameters. Also, results reveal that the absorption frequency is in the terahertz range and shifts to the higher (lower) energies by increasing the electric (magnetic) field. The resonant peak value of the linear optical absorption decreases by increasing the wires' radius, the distance between wires, and the Al composition, however, it changes non-monotonically with the number of wires. Also, the optical absorption reduces with the increase of the electric field and changes non-monotonically with the magnetic field. Manuscript profile