Bandwidth tunable polarization converter in terahertz band based on Ge2Sb2Te5 composite metasurface

We present the design of a terahertz-band tunable polarization converter based on a Ge2Sb2Te5 (GST) composite metasurface. The device comprises a GST composite metasurface, a polyimide (PI) dielectric layer, and a metal substrate. Through structural optimization, a functionalized unit structure is proposed, integrating an open metal ring with embedded GST blocks to achieve the bandwidth-shifting function. Simulation results demonstrate that the proposed structure achieves a bandwidth shift from 2.09 to 3.62 THz to 3.98 to 4.99 THz while maintaining a polarization conversion ratio (PCR) exceeding 95%. We provide a feasible pathway for developing dynamically reconfigurable terahertz polarization modulation devices, which hold promise for applications in terahertz communication, sensing, and imaging.