| In this thesis we investigate the interaction of a nanoscopic dielectric particle (a.k.a. nanoparticle) with a transparent microsphere. We are particularly interested in the effect which a nanoparticle has on the so called photonic atom modes (a.k.a. Whispering gallery modes). Our investigation is both theoretical and experimental.; Theoretically we treat the interaction through first order perturbation theory. The developed theory allows us to derive equations for the shift in the Photonic Atom Resonances. The shift due to multiple nanoparticles is included though a non-interacting sum.; To test our theory we have constructed experiments in which the resonances are stimulated by evanescent coupling to the guided waves in an optical fiber. Instead of creating artificial nanoparticles we have utilized naturally occurring protein molecules which are well characterized by x-ray crystallography. Theory and experiment are in good agreement.; A surprising result is the extreme sensitivity of resonance shifts to protein adsorption. We demonstrate that less than one thousandth of a monolayer of Bovine Serum Albumin (BSA, approximately 4 nm in size) can be sensed. This sensitivity is currently unprecedented for a bio-molecule adsorption, and appears to increase inversely with the microsphere radius. The inverse dependence on radius is borne out theoretically. We anticipate the possibility of observing a single protein adsorption event, and thereby determining the polarizability of a protein molecule.; Near the end of my work I began to investigate the sensitivity to smaller protein molecules. A few of these measurements are presented. |
