Abstract
The main theme of this research is to implement a tunable microsphere resonator platform with an ability of manipulating the coupling distance between a polystyrene microsphere (resonant cavity) and a rib waveguide through a controllable dielectrophoretic (DEP) force on an inhomogeneous structure. The microsphere is suspended in liquid sealed in between two transparent conductive plates. One is coated with amorphous Si and the other is with an SU-8 waveguide structure. First, we use the image-controlled dielectrophoresis for moving the microsphere near the rib waveguide; then, the microsphere will be attracted by the rib and stop in the center of the rib waveguide by a localized DEP on the inhomogeneous structure (rib edge). By changing the applied voltage, the coupling distance between the microsphere and the single-mode rib waveguide is continuously adjustable. Through measuring the waveguide transmittance spectra at different biased voltages across the top and bottom plate, the PSB microsphere is able to be operated either at the over-coupling, near critical-coupling or under-coupling condition. The intrinsic quality factor is estimated to be 26707.