Plasmonic transfer of near-field light from subwavelength objects through a gold-nanorod chain

Abstract

Plasmonics-based nanoimaging techniques have recently attracted significant attention owing to their ability to confine light to the nanoscale for super-resolution imaging. A recent report has theoretically predicted that a plasmonic nanolens, a well-designed array of metallic nanorod chains, can produce a magnified color image of subwavelength objects through a plasmonic transfer of near-field light as a new class of nanoimaging technique. In this study, we fabricate a gold-nanorod chain through a self-assembly method to experimentally validate this concept, and observe the plasmonic transfer of near-field light from subwavelength objects, which demonstrates the significant potential of plasmonic nanolens for super-resolution imaging.

Tapered arrangement of metallic nanorod chains for magnified plasmonic nanoimaging

“…In order to correctly fabricate the nanorod chains, we started with a theoretical optimization of the fabrication parameters. For this purpose, we first calculated the near-field intensity spectrum of an isolated single silver nanorod by the finite-difference time-domain (FDTD) method, under the similar conditions that we used in our previous report for a gold nanorod 15 . In the process of optimizing the size of individual nanorods, we found that a 150-nm-long silver nanorod with 60 nm diameter shows plasmon resonance in the center of the visible range as shown in Fig.…”

“…This is the reason why a plasmonic nanolens has not yet been experimentally demonstrated. In order to show the experimental feasibility of a plasmonic nanolens, we first started with a simplified structure to prove image transfer through a nanorod chain 15 . In our previous study, we demonstrated that a single gold nanorod chain can transfer near-field light originated from a nano-sized optical source of quantum dots (QDs) to a distance much larger than the diffraction limit of light 15 .…”

“…In order to show the experimental feasibility of a plasmonic nanolens, we first started with a simplified structure to prove image transfer through a nanorod chain 15 . In our previous study, we demonstrated that a single gold nanorod chain can transfer near-field light originated from a nano-sized optical source of quantum dots (QDs) to a distance much larger than the diffraction limit of light 15 . In that study, we fabricated a nanorod chain by aligning chemically synthesized gold nanorods with template-assisted self-assembly method, and observed an image of QDs placed at one end of the nanorod chain by detecting the scattered light at the other end of the nanorod chain, which was transferred through the plasmonic coupling of the neighboring nanorods in the nanorod chain.…”

“…At the same time, in order to overcome the issue of precise control in our previous study, we adopted a different and improved technique to fabricate the nanorod chains. First, we chose silver as the nanorod material, which covers broader plasmonic resonance in the visible range than the gold 9,15 . Then, in order to precisely control the length of individual nanorods as well as the inter-nanorod gaps, we synthesized long silver nanowires and milled out some parts of the silver nanowires at equal intervals using focused ion beam (FIB) to fabricate nanorods of desired length with precise gaps between them.…”