Enhanced chiral sensing by optical whispering gallery mode microresonator

Chiral sensing is essential in biochemistry, biomedicine, and food industries. Traditional chiral sensing mainly focuses on enhancing the chiral near fields, where the quality factor of the resonator has largely been ignored. Here, we propose a whispering gallery mode (WGM) optical microresonator to enhance the chiral signal by exploiting its high quality factor. The enhancement factor in the WGM resonator is linearly dependent on the quality factor of the microresonator and exponentially increases with the decreasing thickness of the chiral analyte. Based on this, we achieve a chiral enhancement factor of more than two orders of magnitude, which features a background-free chiroptical signal. Our results open a route to attain highly sensitive chiral sensing based on the WGM optical resonator, which promotes the realization of chiral applications in integrated optics.