Mapping of plasmonic resonances in nanotriangles

Abstract

SummaryPlasmonic resonances in metallic nano-triangles have been investigated by irradiating these structures with short laser pulses and imaging the resulting ablation and melting patterns. The triangular gold structures were prepared on Si substrates and had a thickness of 40 nm and a side length of ca. 500 nm. Irradiation was carried out with single femtosecond and picosecond laser pulses at a wavelength of 800 nm, which excited higher order plasmon modes in these triangles. The ablation distribution as well as the local melting of small parts of the nanostructures reflect the regions of large near-field enhancement. The observed patterns are reproduced in great detail by FDTD simulations with a 3-dimensional model, provided that the calculations are not based on idealized, but on realistic structures. In this realistic model, details like the exact shape of the triangle edges and the dielectric environment of the structures are taken into account. The experimental numbers found for the field enhancement are typically somewhat smaller than the calculated ones. The results demonstrate the caveats for FDTD simulations and the potential and the limitations of “near field photography” by local ablation and melting for the mapping of complex plasmon fields and their applications.

Tip Enhanced Laser Ablation Sample Transfer for Mass Spectrometry

“…The observation that the optimum laser polarization is perpendicular to the tip axis rather than parallel is not consistent with a simple model of apertureless tip enhancement, 67,233 but as noted above, the triangular pyramid shape of the AFM tip may lead to near-field enhancement at the pyramid edges with perpendicular polarization, similar to results from triangular nanoparticles. [234][235][236][237] The fact that the ablation crater is much larger than the tip radius is somewhat unexpected, but is consistent with field enhancement at the pyramidal tip edges. The 600 nm to 1 µm crater diameters are generally consistent with the crater sizes observed in previous studies using aperture 242 and apertureless tips.…”

“…Although optimum tip enhancement typically requires polarization parallel to the tip axis of a pointed probe, 67,233 the tip used in this work is a triangular pyramid that could favor enhancement at the pyramid edges, similar to what has been observed for triangular nanoprisms. [234][235][236][237] The beam was mildly focused…”

Time-resolved optical measurement of thermal transport by surface plasmon polaritons in thin metal stripes

“…In metallic nanoparticles, localized plasmons can lead to hot spots with very high field intensities, leading, e.g., to local photopolymerization of surrounding resist and even to local melting of the nanostructures. 25,26 In this paper, we address propagating SPPs in micron size gold stripes and show how the lateral heat flow and dissipation by SPPs in such systems can be directly measured by optical inspection. 27 Our data demonstrate that the contribution of SPPs can lead to a distinct local temperature increase, illustrating that the decay of SPPs along their propagation path has to be taken into account in the heat management of plasmonic devices.Our experimental set-up is shown in Fig.…”

Fractal aluminum Cayley-trees to design plasmonic ultraviolet photodetectors

“…However, non-spherical nanostructures have received growing interest due to unique spectral lineshapes and features that cannot be achieved by spherical particles such as nanotriangles, nanocubes, and nanostars [13][14][15]. Recently, a successful fractal structure in Y-shape formation was introduced for microwave frequencies and near-infrared region to support strong plasmon resonant modes with multifrequency electromagnetic response [16,17].…”