Vanadium Dioxide Integrated Metasurfaces with Switchable Functionalities at Terahertz Frequencies

Integration of switchable and diversified functionalities into a single metasurface has become an emerging research area that requires dealing with formidable challenges, especially for terahertz (THz) frequencies. Here, polarization‐insensitive and switchable THz metasurfaces are proposed with diversified functionalities that exploit insulator‐to‐metal transition in vanadium dioxide (VO2). The simulations demonstrate that the designed metasurface can be switched from a broadband absorber to a reflecting broadband halfwave plate (HWP). At room temperature, the metasurface efficiently absorbs normally incident waves ranging from 0.562 to 1.232 THz with the total absorption exceeding 90%. Once the temperature is high enough and VO2 is in its fully metallic state, the metasurface becomes a broadband HWP reflecting over 60% of the incident power with the linear polarization conversion efficiency exceeding 95% within the bandwidth of 0.49 THz. Moreover, the broadband performance is sustained over a wide range of incident angles. To extend the functionalities, metasurface supercell made of several VO2 antennas is integrated, consequently achieving directional polarization conversion when VO2 is in its fully metallic state while maintaining broadband absorption at insulating state. The proposed switchable metasurfaces are expected to enable advanced research and smart applications related to other tunable and diverse functionalities at THz frequencies.