Frank Vollmer
Center for Studies in Physics and Biology, Rockefeller University.
| A glass microsphere is able to confine light to its interior volume. The unprecedented narrow linewidth of this optical resonance (Q's ~1010) allows precise measurement of its frequency. Although the resonance is stealth as seen from the outside, an evanescent field extends from the microsphere surface into the surrounding medium. We observe that molecules binding to the surface perturb the resonance by interaction with this evanescent field. The perturbation results in a shift of the resonance frequency. This shift can be measured with such high precision that label-free, single molecule detection seems theoretically possible. We use this high-Q cavity for resonant sensing of nano to microscopic biological objects. The sensitivity of our device also allowed us to discover new physics: We measure an unexpected large pairing effect between Mie particles perturbing the cavity. |
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