Whispering Gallery Mode Microresonators for Biosensing

Abstract

In the field of sensing, WGM microresonators are receiving a growing interest as optical structures suitable for the realization of miniature sensors with high sensitivity. When properly excited, WGM microresonators are able to strongly confine light, by means of total internal reflection,along the equatorial plane near their spherical surface. The corresponding supported resonances show low losses and a high quality factor Q (107-109). These high values of the Q factor make possible the detection of any minute event that occurs on the surface of the spherical microcavity. In fact, any minimum change in the surface of the sphere or in the physical and optical properties of the surrounding environment reduces the Q factor value and modifies the position of the resonancesinside the dielectric microcavity. From a direct measurement of this resonance shift, one can infer the amount of analyte that produces this variation.