ABSTRACT
A switchable metasurface with dual functions of polarization conversion and filtering is proposed in this paper. The designed structure is composed of a medium-metal-medium-metal-medium structure, and VO2 is embedded in the metal metasurface. When VO2 is an insulated state, this structure can perform linear polarization conversion under terahertz wave normal incidence, and it has good asymmetric transmission capabilities. At the range from 2.01 to 2.86 THz, the polarization conversion rate is higher than 93%. When VO2 is in the metallic state, the structure becomes a broadband band-stop filter with a 3 dB bandwidth of 1.73 THz. The polarization conversion and filtering functions of the proposed structure can be converted to each other by changing the external temperature. This switchable multifunction structure provides a new way for the design of terahertz devices.
ABSTRACT
Many modern terahertz systems require dynamic manipulation of a terahertz wave. We proposed a terahertz wave switch based on a Bi2O2Se/Si structure. The transmittance and conductivity characteristics of the Bi2O2Se in a terahertz region have been measured by terahertz time-domain spectroscopy and analyzed using the Drude model. An ON-OFF switching speed as fast as 2 MHz and an extinction ratio as high as 17.7 dB was achieved at an external laser irradiance of 1.3W/cm2. The switching characteristics of the device can be explained by the accumulation of carriers at the interface that induces terahertz wave intense absorption. Our approach can effectively be used to realize a wide range of dynamically tunable terahertz functional devices. This makes its use viable for a range of communication, imaging, and sensing applications.
