Mechanically reconfigurable terahertz polarization converter by coupling-mediated metasurfaces

Free manipulation of electromagnetic waves in the terahertz (THz) band based on metasurface functional devices has been the focus of research in recent years.Among these devices, active metasurfaces have generated extensive research interest due to their reconfigurability.In this work, we demonstrate a mechanically reconfigurable THz polarization converter that consists of two parallel transmissive metasurfaces with a tunable spacing.By mechanically adjusting the coupling strength between the metasurfaces, the orthogonal polarization conversion of the incident linearly polarized THz waves can be tuned.Specifically, the device can be tuned from efficient dual-frequency orthogonal polarization conversion to efficient single-frequency orthogonal polarization conversion.After a gradual decrease in efficiency, it is finally changed to a low transmission state as the gap distance increases from 150 to 800 m.We theoretically analyze the tuning process under different spacings and experimentally verify it using a vector network analyzer.Our proposed design is straightforward and robust, with the potential to find wide applications in THz science and technology.