Surface Plasmon Polariton Scattering, Light Emission, and Diffraction Phenomena of Highly Contoured Gold Mesostructures

The far-field surface plasmon polariton (SPP) activity of Au polyhedron 3D mesostructures (mesopyramids) with highly textured surfaces consisting of cavities, channels, and plateaus has been examined using oil immersion microscopy, reflectivity spectroscopy, photoluminescence spectroscopy, and spinning disc confocal microscopy. Oil immersion microscopy reveals SPP emission in the form of green, red, and yellow hotspots in the cavities. The wavelengths of the emission correlate with the SPP absorption in the reflectivity and photoluminescence spectra of the mesopyramids. Furthermore, the hotspots are spatially located around surface contours on the floors of the surface cavities (submicron features). This surface topography facilitates scattering that enables radiation to propagate into free space. Imaging of the mesopyramids using spinning disc confocal microscopy reveals the presence of square and hexagonal diffraction patterns, which is due to a combination of simultaneous illumination and imaging of the field of view, vertical resolution of the confocal microscope, and the breakdown of the isolation of the holes in the spinning discs due to the curvature of the mesopyramids.