Far-field sub-diffraction optical imaging using near-field illumination by optoplasmonic hybrid materials

Abstract

Here, we propose a method to fabricate large-scale optoplasmonic hybrid materials (OHMs) as a near-field illumination source for sub-diffraction imaging through a traditional optical microscope. An OHM is comprised of a metal/dielectric multilayer coated substrate and a microcylinder (MC) placed on top of the multilayer. Under the dark-field illumination of a traditional optical microscope, the photonic nanojet (PNJ) generated by the MC and the electric field produced on the substrate surface by the photonic–plasmonic interaction work as the near-field illumination source for an object placed on the substrate near the PNJ. High spatial frequencies of the object can be shifted to the passband of the optical microscope and weak scattering signals of the object can be enhanced upon the near-field illumination. Low-contrast objects, such as a 300-nm-diameter SiO2 nanoparticle array, two 100-nm-diameter polystyrene nanoparticles spaced ∼86 nm apart, and Escherichia coli can be resolved using the optical microscope. In addition, the field of view (FOV) is rectangular, the length of the FOV depends on the length of the MC, and the width relates to the diameter of the MC. The proposed method is wide-field, label-free, direct, noninvasive, and far-field, and it presents the potential of super-resolution imaging of unlabeled biological samples using a traditional optical microscope.