Out-of-plane symmetry breaking of terahertz metamaterials for dual-polarization quasi-BIC

This work proposes a gap-opening double-elliptical cylinder metamaterial that achieves dual polarization multi-resonance mode synergistic excitation by introducing out-of-plane symmetric breaking. Under TE polarization, an exceptionally high Q-factor (4.27 × 10 5 ) of quasi-BIC (Mode 1) is realized, with excellent sensing sensitivity of 750 GHz/RIU, whereas two different quasi-BIC modes (called Mode 2 and Mode 3) are gained under TM polarization. In particular, the near-field coupling of Mode 2 and guided-mode resonance (GMR) gives rise to an electromagnetically induced transparency (EIT), whose performance could be flexibly controlled by precisely tuning the structural asymmetry and other relevant parameters, thereby offering versatile spectral tunability. Multipole decomposition and near-field analysis reveal the formation mechanisms of dual-polarization multi-resonance modes. Our results could have application prospects in fields such as beamforming and biomedical sensing.