Demonstration and characterization of distributed multiparticle-induced mode splitting in a microsphere resonator

• We demonstrate and characterize multiparticle-induced MS where the sizes of particles are in a log-normal distribution using microsphere resonators.
• We experimentally confirm that the total linewidth broadening is proportional to the number of adsorbed particles.
• The signal is immune to the angular positions of particles as well as the thermal fluctuations, which exhibits a more robust mechanism.

Recently introduced mode splitting (MS) in whispering gallery mode resonators (WGMRs) has been widely investigated as a highly sensitive sensing scheme. However, distributed multiparticle-induced MS has not been achieved experimentally up to date. Here, we demonstrate and characterize the multiparticle-induced MS where the sizes of detected particles are in a log-normal distribution using a microsphere resonator. We experimentally confirm that the total linewidth broadening is proportional to the number of adsorbed particles. The signal is immune to the angular positions of particles as well as the thermal fluctuations, which exhibits a more robust mechanism. Moreover, the proposed MS mechanism works equally well even under the unresolvable condition. Observation of mode splitting induced by distributed multiparticles provides a new way for concentration detection of nanoparticles in combustion, traffic exhaust and ambient atmosphere.