Fano resonance engineering in mirror-symmetry-broken THz metamaterials

Abstract

We introduce a comprehensive approach to the design of mirror-symmetry-broken terahertz (THz) metamaterials and present both the simulation and experimental results which show the desired asymmetric Fano resonances and electromagnetically induced transparency-like windows. With a full-wave simulation, we find these asymmetry-induced resonance modes possess extremely high quality factors and they broaden with an increase in the structure asymmetry. This phenomenon arises from the destructive interference of a super-radiative bright mode and a sub-radiative dark mode which cannot be excited directly. Surface current and electric field distributions are analyzed to explain the emergence of these Fano resonances. An intuitive mechanical coupled oscillator model is derived to explain the unique line-shape of such Fano resonances. Moreover, large resonant frequency tuning (50 GHz) of Fano resonance has been demonstrated by temperature-induced phase change in liquid crystals. We believe that the Fano resonance in THz metamaterials may serve as a strong building block for passive or active THz elements with potential applications for future detection and sensing systems and devices.