Second‐harmonic far‐field microscopy of random nanostructured gold surfaces

Abstract

We use a scanning far-field optical second-harmonic microscope in reflection mode to image a gold film surface covered with randomly distributed scatterers. We recorded simultaneously images of the first (FH) and second harmonic (SH) signal in the wavelength range of 750-830 nm for different densities of scatterers. The SH images showed localized enhancement (~10 3 the background) in the form of small (~0.7µm) round bright spots that exhibited both wavelength and polarization dependences in their brightness. We concluded that the overall behaviour of the observed phenomenon is related to the overlap of FH and SH eigenmodes.

Modeling of Plasmonic Phenomena in Nanostructured Surfaces

“…The multiple-scattering between the nanoparticles was established through self-consistent calculations of the electric field distributions using a combination of two separate expressions for the involved Green dyadic, valid either for shorter-or longerinteraction distances. In general, the simulations presented here offered qualitatively good agreement with experimental results, 15,16,22,34,38,41,42 indicating that the approach can be used, with certain limitations, for modeling of plasmonic nanodevices.…”

“…41,42 With the variety of experimental results obtained in this context, it is rather important to understand the image formation process. Especially for systems like the curving microrings of organic molecules or enhancement effects from randomly positioned metal nanoparticles.…”

“…One conspicuous detail about the FH images is that the reversed cross-polarized configurations, i.e., (x, y)and (y, x)-configurations, result in exactly the same images that are also more sensitive to polarization than the FH images. Such a striking difference is related to the circumstance that the reversed FH images correspond to the reciprocal SOM configurations that should produce the same images, 41,42 whereas the SH images are produced in the process of nonlinear imaging so that the reversed configurations are not reciprocal. It is also seen that the SH images are considerably more sensitive to the wavelength than the FH images.…”

“…As was previously suggested, the very bright spots in the SH images could occur due to spatial overlap of properly polarized FH and SH eigenmodes. 41,42 The bright spots in SH images are therefore related to the positions of FH and SH eigenmodes both being sensitive to the wavelength. Consequently; the SH bright spots turn out being more sensitive to the wavelength than the FH bright spots.…”

Surface Plasmon Polariton Localization

“…In this context, round and bright spots (∼10 3 the background signal) were reported as a direct evidence of enhanced nanooptical fields (localized SPPs) generated via nonlinear interaction in metal nanostructures. 10 Here, I present an overview of some of the problems, developments, and current progress related with our research in the surface polariton localization phenomena. I begin with an introduction to SPPs in Sec.…”