Nonvolatile Switchable Broadband Polarization Conversion with Wearable Terahertz Chalcogenide Metamaterials

Abstract Polarization is a fundamental characteristic of light waves carrying sensitive measurement and signal communication information. Traditional schemes for advanced controlling polarization impose stringent requirements on material features and obtain merely limited performance. Integration of diversified and switchable functions into monolithic metamaterials has become a rising research field, particularly for the terahertz (THz) spectrum. However, the study on the switchable and wearable polarization meta‐converter with nonvolatile operation stays unexplored. Here, the switching of metamaterial‐induced ultra‐broadband and very efficient reflective linear polarization conversion at the THz frequency is experimentally realized. When the as‐deposited Ge₂Sb₂Te₅ (GST225) capping layer of the proposed converter is in amorphous state, the multilayered metamaterials possess triple neighboring peak resonances, by which the linear incident polarization could be converted to its orthogonal counterpart on reflection. The measured polarization conversion ratio (PCR) under normal incidence is above 0.7 in the spectrum ranging from 0.53 to 1.25 THz. Notably, the strength of PCR can be continuously tuned as gradually transiting the structural state of GST225 from amorphous to crystalline. This continuously switchable converter may pave an avenue for dynamically controlling the THz polarization states and bring more possibilities for flexible meta‐devices in the various applications for THz imaging, spectroscopy, and communications.