Bifunctional terahertz metamaterial device with switchable properties between transmission and broadband absorption

In recent years, metamaterial devices have been developed with dynamically switchable functions between narrowband (or multi-band) and broadband absorption. However, these metamaterial devices cannot switch between transmission and absorption. Inspired by previous research, a bifunctional terahertz metamaterial device with switchable properties between transmission and broadband absorption is proposed. The simulated results show that the switchable functional characteristics of the absorber can be achieved by changing the phase transition property of VO₂. When VO₂ is in the insulating state, there are transmission spectra with a maximum transmittance of 90% and a minimum transmittance of 25% in the frequency range from 1 THz to 10 THz. Meanwhile, transmission spectra be adjusted by controlling the Fermi energy of graphene. When VO₂ is in the metal state, the broadband absorptivity achieves over 90% in the frequency range from 2.54 THz to 7.65 THz. Not only that, the absorption spectra can be continuously adjusted by controlling the conductivity of VO₂ from 20 to 200000 S/m. Alternatively, the proposed bifunctional terahertz metamaterial device can work and show the same absorption spectra when the conductivity of VO₂ is 200000 S/m under TM and TE polarized normal incidences. Our current work could provide a new pathway for further development of transmissive and broadband absorbing types of metamaterial devices in the THz range.