A Thermally Switchable Bifunctional Metasurface for Broadband Polarization Conversion and Absorption Based on Phase‐Change Material

Integrating tunable characteristics and multiple functions into a single metasurface attracts more and more attention. Herein, a reconfigurable bifunctional metasurface is proposed to realize the switch between broadband polarization conversion and absorption. The switchable performance can be achieved by changing the conductivity of phase-change material Ge2Sb2Te5 (GST) in the way of heating. When the conductivity σ of GST is set to 0 Sm−1, the metasurface is a polarizer that can transform the x-polarized wave into the y-polarized wave in the range of 0.53–1.22 THz. Moreover, its polarization–conversion ratio (PCR) is more than 90% from 0.60 to 1.15 THz. As σ increases to 1 × 105 Sm−1, the metasurface absorbs more than 75% of the incident wave from 0.44 to 1.34 THz, which means it is a broadband absorber. In addition, the performance of the metasurface is verified by simulation, experiment, and theory. Through comparison, the three results have a high fitting degree. The reconfigurable metasurface provides a new way to develop switchable photonic devices in the terahertz frequency region.