  Fano resonance is widely discussed in designing novel terahertz components,
such as sensors, filters, modulators, and group delay modules. Usually, high
quality (Q) factor and flexible tunability of Fano resonance are key
requirements for these applications. Here, we present tunable terahertz Fano
resonance with a Q factor of 2095 at 0.439 THz in coupled terahertz
whispering-gallery-mode resonators (WGMRs). Coupling between a relatively low Q
(578) quartz ring and a high Q (2095) silicon ring is employed to generate the
Fano resonance. The resonant frequency of the Fano resonance can be actively
manipulated by tuning the resonant frequency of the high Q WGMR, which is
achieved through utilizing an electrical thermo-optic tuning method, meanwhile,
the resonance intensity of the Fano resonance can be engineered by adjusting
the coupling strength between two WGMRs. This coupled-WGMR scheme delivers high
Q tunable Fano resonance and may contribute to the design of high-performance
configurable terahertz devices.
