Spectral Tuning Of Directional Scattering For High Precision Position Sensing

High precision optical position sensing of a single nanoparticle or a biomolecule is of paramount importance in modern nanometrology, microscopy and medicine. In the context of resolution, the last decade has undergone a revolutionary development achieving localization precision down to few nanometers or even Angstroms, using different linear and nonlinear techniques [1-5]. As a proof-of-concept experiment, we have demonstrated Angstrom lateral localization precision utilizing strongly directional light emission of a single subwavelength dielectric scatterer placed in a tailored electromagnetic field distribution [1]. Silicon nanoparticles, due to their high refractive index, support both electric and magnetic resonances in the visible regime [6-8]. By taking advantage of simultaneous excitation of multiple particle modes and the interference of their emission, a strong directional scattering signal can be observed. When interacting with a selectively tailored inhomogeneous electromagnetic field distribution, different coupling scenarios can be achieved, resulting in strong position dependent lateral directional scattering (see Fig. 1).