Abstract
In this study, an integrated operation platform is proposed to study optomechanics of colloidal microsphere resonators on a chip, which solves the issue of difficulty for precisely controlling the coupling between the colloidal microspheres and tapered optical fibers. On this platform, the dielectrophoretic force (DEP) is utilized to capture microsphere resonators and position the microsphere on top of a waveguide for an appropriate optical coupling condition. The coupling condition can be easily and quickly detected through measuring the transmittance of the optical waveguide. This platform can be applied for both solid or liquid microsphere resonators. It shows great measurement stability, and has the potential to be integrated into today's micro-fluid systems as an effective tool for optically probing. In addition, we successfully use this platform to determine the radius of microdroplets with a measurement error down to tens of nanometers, under a consistent ambient temperature. This platform also facilitates the study of resonance-enhanced optomechanics of colloidal microspheres.First, we directly observed an optically induced gradient force and figure out a self-regulation of coupling condition of colloidal microspheres varied by waveguide power. A cavity-enhanced optomechanical bistability of coupling condition was observed, which we believe it was never reported before. Meanwhile, we also observed optically induce local deformation of a spherical microdroplet cavity through our operation platform, and for the first time, we demonstrate nonlinear detuning of the cavity wavelength via the use of tunable laser with low-power excitation.