Observation and characterization of mode splitting in microsphere resonators in aquatic environment

TL;DR

This paper demonstrates for the first time mode splitting in microsphere resonators submerged in water, analyzing how particle size and resonator properties influence the phenomenon, with experimental validation.

Contribution

It introduces the observation of scatterer-induced mode splitting in microsphere resonators in aqueous environments, expanding the applicability of WGM sensing techniques.

Findings

Mode splitting observed in water for microsphere resonators.

Particle size range inducing mode splitting determined.

Experimental confirmation of the phenomenon.

Abstract

Whispering gallery mode (WGM) optical resonators utilizing resonance shift (RS) and mode splitting (MS) techniques have emerged as highly sensitive platforms for label-free detection of nano-scale objects. RS method has been demonstrated in various resonators in air and liquid. MS in microsphere resonators has not been achieved in aqueous environment up to date, despite its demonstration in microtoroid resonators. Here, we demonstrate scatterer-induced MS of WGMs in microsphere resonators in water. We determine the size range of particles that induces MS in a microsphere in water as a function of resonator mode volume and quality factor. The results are confirmed by the experimental observations.