Tunable Fano resonance with ultrahigh peak by bright-dark mode coupling in Dirac semimetal

A dynamically tunable Fano resonance with characteristic symmetric structure consisting of the wire and double-U resonator microstructure at the terahertz region in Dirac semimetal metamaterials was demonstrated. The wire plays dual roles for the exciting resonance: as a player of the bright mode and as crucial part of the inductive-capacitive (LC) resonators that induce the darkmode. The destructive interference between the bright and darkmodes achieves a novel Fano optical response. Different from previous research, we analyze the influence of different refractive index smear layers on the resonance frequency, and a lower refractive index of the materials is more suitable as a high-sensitivity refractive index sensor substrate. Interestingly, the research has shown that the Fano resonance frequency can be dynamically controlled by adjusting the Fermi energy. Moreover, we can also acquire positive group delay of about 23.54 ps with varying the Fermi energy in the proposed structure. These properties may provide guidance for fabricating biological sensors and slow-light devices in the terahertz region. (C) 2019 Optical Society of America