Magnetic-induced dual-function tunable THz polarization conversion metamaterial based on Ni-Mn-Sn shape memory alloy films

Due to the improvement in miniaturization and practicability of polarization conversion devices, the terahertz polarization control technology has been paid more and more attention. Nevertheless, a critical factor in restricting its development is short of dynamic and multifunctional materials. Ferromagnetic shape memory alloys (FSMAs) provide a novelty solution for tunable metamaterials because of their excellent recovery deformation, non-contact control, and fast response. Here, a new magnetic-induced tunable THz metamaterial is proposed, composed of Ni-Mn-Sn FSMAs resonator in strip structure, polyimide dielectric, and metal copper substrate. Numerical results reveal that the polarization converter can realize any in a broad band between 1.04 and 1.96 THz by applying different magnetic fields to adjust the elastic deformation of Ni-Mn-Sn. Notably, the device can also realize line circularly polarized light conversion in the range of 0.87–0.92 THz and 2.07–2.12 THz. Compared to the current state-of-the-art double functional polarization converter, the THz converter proposed in this work offers benefits in many respects, including the 61.3% relative bandwidth and high conversion efficiency. Our study provides an excellent strategy to develop actively tunable and multifunctional THz compact devices.