Emerging Methods for Controlling Hot Carrier Excitation and Emission Distributions in Nanoplasmonic Systems

Concentrated optical fields in plasmonic metal nanostructures generate high densities of excited charge carriers, which can be extracted or emitted into surrounding media for a variety of physical, chemical, and biological applications. However, the detailed geometry-and field-dependent photoexcitation mechanisms determining the spatial, temporal, vector momentum, and energy distributions of these carriers in nanoplasmonic systems are still under investigation. Gathering insights from recent studies with nanoscale spatial, femtosecond temporal, and/or angle resolved momentum resolution, we survey several emerging methods for geometrical design and active optical control of nanoplasmonic hot carrier excitation and emission distributions. Uniform dielectric coatings, for example, provide a means of blocking or regulating hot carrier emission, while nonuniform coatings can provide nanoscale spatial selectivity. Nanoscale site selectivity can also be actively controlled on ultrafast time scales by optically addressing different polarization-and/or frequency sensitive hot spots, particularly with sharp nanocathode geometries such as nanostars. Furthermore, the nanoplasmonic geometry and the corresponding internal vs surface electric field distributions significantly influence the fundamental bulk-vs surface-like photoexcitation mechanisms, with dramatic effects on the excited carrier distributions and dynamics. Finally, energy-resolved pump- probe photoemission studies clarify the tens-of-femtosecond time scales relevant for hot carrier extraction.

Automated summary

This article summarizes the methods for controlling the excitation and emission distributions of hot carriers in nanoplasmonic systems, including geometric design and optical control. It also emphasizes the significant influence of nanoplasmonic geometry and electric field distributions on the carrier dynamics and distributions.