Abstract
An emitter near a surface induces an image dipole that can modify the observed emission intensity and radiation pattern. These image-dipole effects are generally not taken into account in single-emitter tracking and super-resolved imaging applications. Here we show that the interference between an emitter and its image dipole induces a strong polarization anisotropy and a large spatial displacement of the observed emission pattern. We demonstrate these effects by tracking the emission of a single quantum dot along two orthogonal polarizations as it is deterministically positioned near a silver nanowire. The two orthogonally polarized diffraction spots can be displaced by up to 50 nm, which arises from a Young’s interference effect between the quantum dot and its induced image dipole. We show that the observed spatially varying interference fringe provides a useful measure for correcting image-dipole-induced distortions. These results provide a pathway towards probing and correcting image-dipole effects in near-field imaging applications.
Highlights
An emitter near a surface induces an image dipole that can modify the observed emission intensity and radiation pattern
This phenomenon can have a major impact on the accuracy of single-particle tracking. We experimentally demonstrate these effects by deterministically positioning an individual quantum dot in the vicinity of a silver nanowire and tracking the emission simultaneously along two orthogonal polarizations
We can attain an intuitive understanding of the system in the limit in which the emitter is sufficiently close to the wire such that the surface is approximately flat and the distance is small compared with the wavelength of light
Summary
An emitter near a surface induces an image dipole that can modify the observed emission intensity and radiation pattern. We show that the interference between an emitter and its image dipole in a nanostructure can induce substantial polarization-dependent changes to both the intensity and position of the emitter’s far-field diffraction spot This phenomenon can have a major impact on the accuracy of single-particle tracking. The diffraction spots measured at polarizations parallel and perpendicular to the nanowire can be displaced by as much as 50 nm, which is much larger than the expected accuracy of single-emitter tracking techniques[6] This position displacement occurs even at distances exceeding 200 nm from the wire surface, and is the result of a Young’s interference effect between the emitter and its image dipole. These results provide a better fundamental understanding of image-dipole effects in nanostructures and offer a promising route to improve the accuracy of near-field probing and sensing applications
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