Heat and Temperature Localization via Fabry–Pérot Resonances at the Tip of a Nanofocusing Cone

Abstract

Nanofocusing of electromagnetic (EM) energy is an emblematic effect that guides EM energy along plasmonic conical structures, effectively focusing it at its nanometer‐sized extremity. However, EM energy nanofocusing could also be accompanied by (often disregarded) heating. Here, rigorous 3D finite element method simulations of a plasmonic conical structure were performed with a finite‐size apex excited by a continuous wave radially polarized beam over visible and near‐infrared wavelengths. Together with broadband nanofocusing the presence of narrowband Fabry–Pérot (FP) like resonances is demonstrated. Importantly, FP‐like resonances yield strong temperature localization that adds to the broadband nanofocusing component, providing an extra degree of freedom in tuning the temperature localization through proper selection of the structure dimensions suitable for applications in Raman, electron emission spectroscopies or sharp‐tip nanofabrication strategies.

Hyper-Branched Gold Nanoconstructs for Photoacoustic Imaging in the Near-Infrared Optical Window

“…The poor photostability of GNRs and GNSTs could be explained by the reshaping behavior of anisotropic GNCs below their melting temperature . In addition, localized E-field enhancement at the tips of anisotropic GNCs results in high local temperatures at the construct tips. , (Figure S8). The high-temperature localization can cause the construct tips to melt more easily than the body of the construct, , leading to the morphological transition of the anisotropic shape into spheres via atomic diffusion, , followed by decreased optical absorption and subsequent PA signal decay.…”

“…In addition, localized E-field enhancement at the tips of anisotropic GNCs results in high local temperatures at the construct tips. , (Figure S8). The high-temperature localization can cause the construct tips to melt more easily than the body of the construct, , leading to the morphological transition of the anisotropic shape into spheres via atomic diffusion, , followed by decreased optical absorption and subsequent PA signal decay. In contrast, small GNSs that were used in HBGNC synthesis have been shown to exhibit a melting temperature comparable to that of bulk gold and a high photodamage threshold of approximately 50 mJ cm –2 under pulsed laser illumination .…”