Vanadium dioxide-assisted multifunctional terahertz devices platform: modulator, polarization converter, and biosensor

Exploiting the phase transition of vanadium dioxide (VO2), a switchable terahertz multifunctional device integrating narrowband absorption and broadband polarization switching was proposed in our study. The transformation of VO2 from insulating state to metallic state can realize different functions. When VO2 was in metal state, the metamaterial device exhibited an absorption effect exceeding 90% in the range of 1.96 to 4.06 THz, and its amplitude was tunable via changing the conductivity of VO2. Further, the modulation depth reached 171%. This device was also used as a broadband cross-polarization converter, achieving more than 97% cross-polarization conversion in the range of 2.03 to 3.93 THz. When VO2 was in insulating state, a narrow-band absorption peak with an absorption rate exceeding 94% was obtained, and the device can be used as a biosensor with a sensitivity of 363 GHz/RIU. The designed THz metamaterials have broad application prospects in modulation, sensing, radar communication, and other fields.