Vanadium dioxide metasurface with dual functionalities of an optical switch and a sensor

This paper introduces a polarization-independent terahertz metasurface based on the phase transition characteristics of vanadium dioxide (VO2), featuring dual-frequency asynchronous optical switches and sensors. The sub-unit of the device consists of a silicon dioxide substrate, with a cross structure composed of VO2 and gold. When VO2 is in the metallic state, the S1 switch is "off," while the S2 switch can be "on." Conversely, when VO2 is in the dielectric state, the S2 switch is "off," while the S1 switch can be "on." The numerical results indicate that the extinction ratio of the S1 switch can exceed 19 dB, and that of the S2 switch can exceed 16 dB. The sensitivity of the S1 sensor can reach 135277.17 nm/RIU, and that of the S2 sensor can reach 31755.23 nm/RIU, with quality factors (FOM) of 194.01 and 16.57, respectively. The proposed device offers new insights for the design of future terahertz filters, optical switches, and sensors. We believe that the metasurface structure proposed in this paper can be used for optical switching, optical modulation, optical memory, and large-scale optoelectronic integrated circuits.