Femtosecond Laser Irradiation for Hot Spots Mapping on the Surface of Plasmonic Nanostructure

In this research, we present a novel method for visualising plasmonic `hot spots` upon plsmonic surfaces of gold nanostructures. Femtosecond laser pulses have been used to map the locations of localized high-intensity electromagnetic fields i.e. the locations of hot spots. Upon irradiation with 800 nm femtosecond laser pulses, which may be linearly or circularly polarised, it is possible to reveal the locations of plasmonic hot spots since the nanostructures are physically damaged i.e. undergo melting by the intense heat generated by femtosecond laser pulse irradiation [1, 2]. SEM microscopy was used subsequently to map the surface of the nanostructures to show which areas have been damaged, and hence reveal the locations of the hot spots. 2D arrays of quadric units (arranged in a racemic fashion) consisting of two patterns: gammadions and G-like shapes have been used as plasmonic chiral nanostructures. It has been found that irradiation with linearly polarised light affected segments that are perpendicular to the polarisation direction of the incident beam. However, irradiation with circularly polarised light affected both horizontal and vertical segments of the nanostructures regardless of the sense of individual features (i.e. left-handed or right-handed) or the sense of the circular polarisation of the incident beam (i.e. clockwise or counter-clockwise). Hence, no enantio-selectivity was observed.

Author(s): Nadia A. Abdulrahman

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