Active control of Fano resonance in side-coupled resonator-cavity systems

Abstract

The study delves into actively controlling Fano resonance within a single-mode microstrip cavity, coupled with a split ring resonator (SRR) incorporating a varactor diode. This resonance arises from the interference between the SRR and a Fabry–Pérot cavity, resulting in a sharply asymmetric transmission spectrum. The varactor diode, situated within the SRR gap, is biased electrically via an external DC voltage source. Through manipulation of this bias voltage, both the transmission frequency and amplitude of the pronounced Fano resonance can be dynamically adjusted. Notably, a significant frequency shift of 345 MHz is achieved, accompanied by a transmission modulation depth of up to 34.2 dB. Moreover, at the Fano peak frequency of 2.65 GHz, the composite SRR-cavity structure exhibits a notable change in group delay, shifting by 21.3 ns with the bias voltage varying from 5 V to 2.6 V. These findings hold promise for the development of electrically controlled functional photonic devices, facilitating their adaptability and versatility in practical applications.