Journal
NANOPHOTONICS
Volume 12, Issue 10, Pages 1931-1942Publisher
WALTER DE GRUYTER GMBH
DOI: 10.1515/nanoph-2023-0120
Keywords
electron source; nanoparticle; nanostructure; photonics; plasmonics; strong-field ionization
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In this study, the generation and dynamics of photoelectrons from plasmonic nanostructures under intense laser pulses in the infrared regime were investigated. It was found that the contribution from direct photoemission significantly increased, suggesting the potential for developing compact tunable electron sources.
The efficient generation, accurate detection, and detailed physical tracking of energetic electrons are of applied interest for high harmonics generation, electron-impact spectroscopy, and femtosecond time-resolved scanning tunneling microscopy. We here investigate the generation of photoelectrons (PEs) by exposing plasmonic nanostructures to intense laser pulses in the infrared (IR) spectral regime and analyze the sensitivity of PE spectra to competing elementary interactions for direct and rescattered photoemission pathways. Specifically, we measured and numerically simulated emitted PE momentum distributions from prototypical spherical gold nanoparticles (NPs) with diameters between 5 and 70 nm generated by short laser pulses with peak intensities of 8.0 x 10(12) and 1.2 x 10(13) W/cm(2), demonstrating the shaping of PE spectra by the Coulomb repulsion between PEs, accumulating residual charges on the NP, and induced plasmonic electric fields. Compared to well-understood rescattering PE cutoff energies for strong-field photoemission from gaseous atomic targets (10x the ponderomotive energy), our measured and simulated PE spectra reveal a dramatic cutoff-energy increase of two orders of magnitude with a significantly higher contribution from direct photoemission. Our findings indicate that direct PEs reach up to 93 % of the rescattered electron cutoff energy, in contrast to 20 % for gaseous atoms, suggesting a novel scheme for the development of compact tunable tabletop electron sources.
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