Tunable Fabry-Perot resonators with embedded graphene from terahertz to near-infrared frequencies.

Fabry-Perot resonators with inserted graphene are proposed for efficient reflectance modulation from terahertz to near-infrared frequencies. The resonators' structure is simple and consists of the Bragg top mirror, the cavity with the graphene, and the metallic bottom mirror. Reflectance from the cavities is electrically controlled by adjusting the Fermi level in the graphene. At near-infrared and terahertz frequencies, the amplitude modulation of the reflectance is dominant. On the other hand, tuning at mid-infrared frequencies is based on the spectral modulation of cavity resonances. By the impedance matching of resonators to a surrounding medium, the achieved insertion loss and modulation depth approach zero and 100%, respectively.