Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

Abstract

We introduce a simple, fast, efficient and non-destructive method to study the optical near-field properties of plasmonic nanotriangles prepared by nanosphere lithography. Using a rectangular Fourier filter on the blurred signal together with filtering of the lower spatial frequencies to remove the far-field contribution, the pure near-field contributions of the optical images were extracted. We performed measurements using two excitation wavelengths (532.1 nm and 632.8 nm) and two different polarizations. After the processing of the optical images, the distribution of hot spots can be correlated with the topography of the structures, as indicated by the presence of brighter spots at the apexes of the nanostructures. This technique is validated by comparison of the results to numerical simulations, where agreement is obtained, thereby confirming the near-field nature of the images. Our approach does not require any advanced equipment and we suggest that it could be applied to any type of sample, while keeping the measurement times reasonably short.

Design of a Plasmonic Platform to Improve the SERS Sensitivity for Molecular Detection

“…The main advantage of stencil techniques is the low-cost fabrication of large arrays of metallic nanostructures with controlled size, shape, and interparticle distance. Recently, we used this technique in the fabrication of a hexagonal array of plasmonic gold nanotriangles on the glass substrate with unique dimension [27], which led to an efficient study of the localized surface plasmon resonance (LSPR) of the nanotriangles due to the spatial confinement of the electric field. Stencil techniques may be used as the most suitable for the fabrication of our proposed complex plasmonic platform composed of SPNs and LPNs as compared with self-organized techniques, given the preferential close-packed nature of hexagonal patterns.…”