An Integrated Operational Platform for Studying Colloidal Microsphere and Microdroplet Resonators

In this study, an integrated operation platform is proposed to study colloidal microsphere and microdroplet resonators on a chip. Via varying dielectrophoretic force induced on a specially designed concentric ring electrode, spherical optical resonators are able to be precisely controlled on their position relative to an integrated waveguide with resolution down to tens of nanometer, which is crucial to determine the coupling condition of the resonator. A solid-state polystyrene microsphere and an immersion oil droplet are demonstrated with ability to be freely operated in undercoupling, critical coupling, and overcoupling regimes. Through this platform, a metrology technique is reported to precisely measure the radius of a microdroplet by examining the resonant modes. This platform could be a useful tool to study optical resonance of spherical objects dispersed in water.