Optical coupling of spherical microresonators with tapered fibers for chemical/biomedical applications

A system consisting of a microbubble coupled with a tapered fiber is designed in order to detect different concentrations of an aqueous sodium chloride (NaCl) solution. The microbubble whispering gallery modes WGMs are selectively excited by means of a pair of identical long period fiber gratings (LPGs) placed on both taper ends. The simulation of the set-up gives a numerical proof-of-concept toward the exploitation of sensing applications in medical diagnostic and environment monitoring. The response of the microbubble, in terms of the different WGMs resonance detuning shifts, to an increasing NaCl concentration is investigated. The simulated results promise interesting applications.