Tunable triple-band and broad-band convertible metamaterial absorber with bulk Dirac semimetal and vanadium dioxide.

We propose a convertible metamaterial device with triple-band and broad-band characteristics based on bulk Dirac semimetal (BDS) and vanadium dioxide (VO2). When VO2 is in the fully insulating state, the proposed convertible device presents three distinctive absorption peaks in terahertz (THz) range with absorptance >98%. Absorptance spectra analysis shows a clear independence on the conductivity of VO2 when the device act as a triple-band absorber. When VO2 is in the fully metallic state, the convertible device expresses a broad-band absorption. In addition, this broad-band absorptivity can be continuously adjusted by changing the conductivity of VO2. Importantly, without making any changes to the structure parameters, the system exhibits unique convertible mechanism from triple-band to broad-band absorption. Electric field distributions are further discussed to explore the physical origin of this convertible absorber. Benefitting from the variable Fermi level of BDS, resonance frequency can be dynamically tuned. This design approach combined the use of BDS and VO2 not only paves a new way to realize a convertible absorber from triple-band to broad-band absorption, but also enables us to control the resonance frequency and absorption intensity in THz range. It is believed that the tunable converter provides plentiful applications such as modulator, energy harvesting and optic-electro switches. [ABSTRACT FROM AUTHOR]