Design of separately tunable terahertz two-peak absorber based on graphene

• A separately tunable terahertz (THz) two-peak absorber based on graphene is presented.
• The controlling voltage is applied between the reflector and two separated surface electrodes to tune the Fermi level of graphene. And thus, these two absorption peaks can be separately tuned by the voltage.
• The simulation results show that the absorption of low-frequency and that of high-frequency are 95.5% and 90.0%, respectively. And the maximum modulation depths of them are 49% and 71%, respectively.
• The absorber is insensitive to polarization and has good absorption at large angle.
• This study offers a new way for development of frequency selective detectors.

A separately tunable terahertz (THz) two-peak absorber based on graphene is presented. From bottom to top, the absorber contains four layers, i.e., gold reflector, graphene patch array, polyimide and metal split-ring resonator (SRR) array layer. The controlling voltage is applied between the reflector and two separated surface electrodes to tune the Fermi level of graphene. As a result, these two absorption peaks can be separately tuned by the controlling voltages. The finite integral technique (FIT) is used to study the absorption theory and modulation mechanism. The simulation results show that the absorption of low-frequency and that of high-frequency are 95.5% and 90.0%, respectively. And the maximum modulation depths of them are about 49% and 71%, respectively. Moreover, the absorber is insensitive to polarization and still has good absorption at large angle. The separately tunable THz two-peak absorber offers a new way for the development of frequency selective detectors working in the range of microwave, THz and infrared.

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