Experimental observation of Fano-like resonance in a whispering-gallery-mode microresonator in aqueous environment

Abstract

We report on the transmission spectra of a sausage-like microresonator (SLM) in aqueous environment, where a fiber taper is used as a light coupler. The transmission spectra show an interesting dependence on the coupling position between the SLM and the fiber taper. When the SLM is moved along the fiber taper, the line shape can evolve periodically among symmetric dips, asymmetric Fano-like resonance line shapes, and symmetric peaks. A coupled-mode theory with feedback is developed to explain the observation. The observation of Fano-like resonance in aqueous environment holds great potential in biochemical sensing.