Tunable optical resonators by manipulating polystyrene microspheres through image-controlled dielectrophoretic force

An image-controlled dielectrophoretic (ODEP) optofluidic system is demonstrated to manipulate microsphere resonators in an aqueous medium. Through this platform we can freely position the microshere resonator near a waveguide to manage the coupling condition. The spectral analysis shows the microsphere resonator can be operated in the under-coupling, critical coupling and over-coupling regimes.