Fano resonance with high Q and figure of merit in terahertz band based on structural perturbation

Fano resonance with high quality (Q) factor and figure of merit (FoM) has significant application prospects in biosensors and lasers. However, most of the previous studies achieve Fano resonance with high Q and FoM by directly regulating the structural asymmetry, which needs high processing precision. To maximize the Q factor of a given resonator, the best constituent material could be a hypothetical perfect electrical conductor (PEC) without ohmic losses. Here, we can indirectly regulate the asymmetry of the structure by perturbation between structures. At low asymmetry, PEC double split rings can obtain high Q factor of 374 and FoM of 257 by adjusting structural asymmetry based on structural perturbation. These are significant for Fano resonances of extremely low-loss and low ohmic losses practical application in the THz band.