Plasmonic nanoparticle assemblies offer unique opportunities for controlling energy transfer at the nanoscale. Here, we demonstrate the ability of deterministic plasmonic arrays to control energy transfer in three key areas: 1) non-linear wave mixing of incident light; 2) structure-dependent circular dichroism; and 3) spatial localization of electromagnetic energy to nanoscale volumes. Single-particle second harmonic generation (SHG) imaging techniques developed in our lab provide high spatial accuracy and precision along with femtosecond time resolution for examining plasmonic assemblies. Femtosecond time-resolution is achieved by employing a sequence of phase-locked laser pulses to examine the nanostructures. Phase-stabilized laser pulse replicas are generated collinearly and used for nonlinear optical imaging by controlling the inter-pulse delay with attosecond accuracy. The phase stability of the pulse replicas persists for several hours, greatly exceeding the requirements for single-particle pump-probe measurements. These phase-stable pulse sequences have been employed to study a series of linear plasmonic nanostructures formed by surface-directed assembly. The results indicate that the position of the electromagnetic hot spot can be determined with an error as small as one nanometer, while simultaneously quantifying the polarization state of harmonic waves. The new experimental imaging capabilities are expected to impact significantly the development of structural nanophotonics, including controlling nanoscale energy transfer.

Imaging nanoscale energy transfer at the limits of temporal resolution and spatial accuracy

249th National Meeting (2015)

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