Self-optimization of plasmonic nanoantennas in strong femtosecond fields

Liping Shi, Bianca Iwan, Rana Nicolas, Quentin Ripault, J.R. Andrade, S. Han, Hyunwoong Kim, Willem Boutu, Dominik Franz, Torsten Heidenblut, Carsten Reinhardt, Hubertus M.J. Bastiaens, G.T. Nagy, Ihar Babushkin, Uwe Morgner, Seung-Woo Kim, Günter Steinmeyer, Hamed Merdji, M. Kovacev

Research output: Contribution to journalArticleAcademicpeer-review

16 Citations (Scopus)
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Abstract

Plasmonic dimer nanoantennas can significantly boost the electric field strength in the gap region, allowing for a modification of the feed gap geometry by femtosecond laser illumination. Using resonant bowtie antennas to enhance the electric field of a low-fluence femtosecond oscillator, here we experimentally demonstrate highly localized reshaping of the antennas, resulting in a self-optimization of the antenna shape. From high-resolution scanning electron micrographs and two-dimensional energy dispersive x-ray maps, we analyze the near-field enhanced subwavelength ablation at the nanotips and the resulting deposition of ablated materials in the feed gap. The dominant ablation mechanism is attributed to the nonthermal transient unbonding of atoms and electrostatic acceleration of ions. This process is driven by surface plasmon enhanced electron emission, with subsequent acceleration in the vacuum. This ablation is impeded in the presence of an ambient gas. A maximum of sixfold enhancement of the third-harmonic yield is observed during the reshaping process.
Original languageEnglish
Pages (from-to)1038-1043
JournalOptica
Volume4
Issue number9
DOIs
Publication statusPublished - 29 Sep 2017

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