Self-optimization of plasmonic nanoantennas in strong femtosecond fields

Liping Shi (1, 2) , Bianca Iwan (2, 3, 4) , Rana Nicolas (3, 4) , Quentin Ripault (3, 4) , Jose R. C. Andrade (1) , Seunghwoi Han (5) , Hyunwoong Kim (5) , Willem Boutu (3, 4) , Dominik Franz (3, 4) , Torsten Heidenblut (6) , Carsten Reinhardt (7) , Bert Bastiaens (8) , Tamas Nagy (1) , Ihar Babushkin (1) , Uwe Morgner (1) , Seung-Woo Kim (9) , Günter Steinmeyer (10) , Hamed Merdji (3, 4) , Milutin Kovacev (1)

1 IQ - Institut für Quantenoptik [Hannover]
2 QUEST - Centre for Quantum Engineering and Space-time Research
3 LIDyl - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
4 ATTO - Attophysique
5 KAIST - Department of Electrical Engineering [Korea Advanced Institute of Science and Technology]
6 Institut für Werkstoffkunde, Leibniz Universität Hannover,
7 Laser Zentrum Hannover
8 MESA+ - Institute for Nanotechnology
9 KAIST - Korea Advanced Institute of Science and Technology
10 MBI - Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie

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.

Domains: Physics [physics]

Liping Shi, Bianca Iwan, Rana Nicolas, Quentin Ripault, Jose R. C. Andrade, et al.. Self-optimization of plasmonic nanoantennas in strong femtosecond fields. Optica, 2017, 4 (9), ⟨10.1364/OPTICA.4.001038⟩. ⟨cea-01613485⟩