Progress in Multifunctional Tunable Terahertz Metasurface Waveplates

Terahertz (THz) waves, as electromagnetic radiation situated between microwaves and optical waves, possess distinct advantages including strong penetration capability, low photon energy, broad bandwidth, and fingerprint spectral characteristics, demonstrating significant application potential in the fields of communication, imaging, and sensing. This paper elaborates on multifunctional tunable terahertz metasurface waveplates that incorporate various tuning mechanisms including electrical, optical, thermal, mechanical, and chemical modulation to achieve dynamic multifunctional integration. These waveplates not only demonstrate efficient polarization conversion and beam manipulation across broad bandwidths, but also exhibit advantages of low loss, high efficiency, reconfigurability, and integration capability. Although current research still faces challenges including fabrication difficulties in low-frequency bands, relatively high loss in high-frequency ranges, and the need for improved response speed and tuning range of modulation mechanisms, the development and applications of dynamically tunable terahertz metasurface waveplates remain critically important, with expected breakthroughs in tuning range, response speed, performance optimization, and integration, thereby providing crucial support for advancing terahertz technologies.