Tapered arrangement of metallic nanorod chains for magnified plasmonic nanoimaging

Plasmonic nanolens, a 3-dimensional tapered arrangement of metallic nanorod chains, holds a great promise as a new plasmonics-based optical nano-imaging technique. While multiple nanorod chains can transfer the near-field signal originating from a sample to an image at a distance larger than a micro-meter, where each nanorod chain contributes in forming one pixel in the image, the tapered arrangement of the nanorod chains with a certain taper angle allows image magnification. We experimentally demonstrate the feature of image formation and magnification in a nanolens by fabricating a tapered arrangement of two silver nanorod chains, which were separated by a distance smaller than the diffraction limit at one end and larger than the diffraction limit at the other end. We placed two nano-sized optical sources of quantum dots near the first ends of the chains, which served as two subwavelength objects. In the optical measurement, we demonstrated that the unresolved subwavelength optical sources could be imaged at the other ends of the chains and were well resolved in accordance with the magnification feature of a nanolens. This verification is an experimental proof of the image magnification, and an important step toward the realization of plasmonic nanolens.