We propose the use of an optically trapped, dye doped polystyrene microspherefor spatial probing of the refractive index at any position in a fluid. Wedemonstrate the use of the dye embedded in the microsphere as an internalbroadband excitation source, thus eliminating the need for a tunable excitationsource. We measured the full width at half maximum of the TE and TM resonances,and their frequency spacing as a function of the refractive index of theimmersion fluid. From these relations we obtained an absolute sensitivity of5e-4 in local refractive index, even when the exact size of the microsphere wasnot a priori known.
展开▼
