Observation of nondegenerate cavity modes for a distorted polystyrene microsphere

Nondegenerate azimuthal morphology-dependent resonances are observed for a distorted, fluorescently labeled polystyrene microsphere levitated in a quadrupole ion trap. Modeling the individual resonances by using perturbation theory allows a determination of quadrupole and octupole distortion parameters. The particle's shape changes slowly over the course of the measurement and eventually becomes spherical. The morphological changes are facilitated by laser heating of the particle above the polystyrene glass transition temperature. We demonstrate a method of transforming a trapped particle to a sphere and rendering its azimuthal modes degenerate.