Development of a terahertz metamaterial polarization converter with multiple tuning modes based on graphene and vanadium dioxide

Abstract

A dynamically tunable terahertz metamaterial polarization converter is proposed. By manipulating the Fermi level of graphene and the conductivity of vanadium dioxide (VO2) flexibly, multiple tuning modes for polarization conversion performance are realized. First, while graphene is in the metallic or insulating state, we can achieve an ideal broadband reflective or an ideal broadband transmissive polarization converter respectively. By manipulating the conductivity of VO2, a modulation depth of 80 % for intensity of the reflected polarization conversion rate (PCRr) and that of 70 % for bandwidth of the transmissive polarization conversion rate (PCRt) can be achieved. Then, while VO2 is in the insulating state, we obtain another broadband transmissive polarization converter. Similarly, we can achieve PCRt intensity modulation by manipulating the Fermi level of graphene. While VO2 is in the metallic state, the device can switch from a broadband polarization converter to a narrow one as the Fermi level of graphene increases. Finally, by manipulating graphene and VO2 simultaneously, the central frequency modulation of PCRt can be obtained with the bandwidth keeping unchanged. Compared with the ones reported recently, our device has some advantages on tuning mode, relative bandwidth, and polarization conversion performance.