Generating Ultrabroadband Deep-UV Radiation and Sub-10 nm Gap by Hybrid-Morphology Gold Antennas

authored by
Liping Shi, José Ricardo Cardoso de Andrade, Ayhan Tajalli Seifi, Jiao Geng, Juemin Yi, Torsten Heidenblut, Frans B. Segerink, Ihar Babushkin, Maria Kholodtsova, Hamed Merdji, Bert Bastiaens, Uwe Morgner, Milutin Kovacev

We experimentally investigate the interaction between hybrid-morphology gold optical antennas and a few-cycle Ti:sapphire laser up to ablative intensities, demonstrating rich nonlinear plasmonic effects and promising applications in coherent frequency upconversion and nanofabrication technology. The two-dimensional array of hybrid antennas consists of elliptical apertures combined with bowties in its minor axis. The plasmonic resonance frequency of the bowties is red-shifted with respect to the laser central frequency and thus mainly enhances the third harmonic spectrum at long wavelengths. The gold film between two neighboring elliptical apertures forms an hourglass-shaped structure, which acts as a "plasmonic lens" and thus strongly reinforces surface currents into a small area. This enhanced surface current produces a rotating magnetic field that deeply penetrates into the substrate. At resonant frequency, the magnetic field is further intensified by the bowties. The resonant frequency of the hourglass is blueshifted with respect to the laser central frequency. Consequently, it spectacularly extends the third harmonic spectrum toward short wavelengths. The resultant third harmonic signal ranges from 230 to 300 nm, much broader than the emission from a sapphire crystal. In addition, the concentration of surface current within the neck of the hourglass antenna results in a structural modification through laser ablation, producing sub-10 nm sharp metallic gaps. Moreover, after laser illumination the optical field hotspots are imprinted around the antennas, allowing us to confirm the subwavelength enhancement of the electric near-field intensity.

Institute of Quantum Optics
PhoenixD: Photonics, Optics, and Engineering - Innovation Across Disciplines
Institute of Materials Science
External Organisation(s)
Carl von Ossietzky University of Oldenburg
University of Twente
Université Paris-Saclay
Nano Letters
No. of pages
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Bioengineering, Chemistry(all), Materials Science(all), Condensed Matter Physics, Mechanical Engineering
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