Fiber Fabry-Perot Interferometer-Based Fano Resonance Coupler for Whispering-Gallery-Mode Resonators

Abstract

In this letter, we present an optical fiber coupler for Fano resonance excitation of whispering gallery modes in microsphere resonators. The coupler can be fabricated conveniently by fusion-splicing an endface-etched fiber with a tapered fiber. Owing to the effective reflections from the fusion splicing-induced in-fiber bubble and the fiber taper tip, Fabry-Perot interference can be observed in the reflective spectrum of the fiber coupler. Since the coupler itself is a Fabry-Perot interferometer, asymmetric Fano resonance can be also excited. The fiber tip-based Fano resonance coupler is simple, compact, and can be used as a probe in the reflection mode, allowing for simple interrogation in biomedical sensing and optical switching applications.