Toward plasmonics with nanometer precision: Nonlinear optics of helium-ion milled gold nanoantennas

Heiko Kollmann, Xianji Piao, Martin Esmann, Simon F. Becker, Dongchao Hou, Chuong Huynh, Lars Oliver Kautschor, Guido Bösker, Henning Vieker, André Beyer, Armin Gölzhäuser, Namkyoo Park, Ralf Vogelgesang, Martin Silies, Christoph Lienau

Research output: Contribution to journalArticlepeer-review

168 Scopus citations


Plasmonic nanoantennas are versatile tools for coherently controlling and directing light on the nanoscale. For these antennas, current fabrication techniques such as electron beam lithography (EBL) or focused ion beam (FIB) milling with Ga+-ions routinely achieve feature sizes in the 10 nm range. However, they suffer increasingly from inherent limitations when a precision of single nanometers down to atomic length scales is required, where exciting quantum mechanical effects are expected to affect the nanoantenna optics. Here, we demonstrate that a combined approach of Ga+-FIB and milling-based He+-ion lithography (HIL) for the fabrication of nanoantennas offers to readily overcome some of these limitations. Gold bowtie antennas with 6 nm gap size were fabricated with single-nanometer accuracy and high reproducibility. Using third harmonic (TH) spectroscopy, we find a substantial enhancement of the nonlinear emission intensity of single HIL-antennas compared to those produced by state-of-the-art gallium-based milling. Moreover, HIL-antennas show a vastly improved polarization contrast. This superior nonlinear performance of HIL-derived plasmonic structures is an excellent testimonial to the application of He+-ion beam milling for ultrahigh precision nanofabrication, which in turn can be viewed as a stepping stone to mastering quantum optical investigations in the near-field.

Original languageEnglish
Pages (from-to)4778-4784
Number of pages7
JournalNano Letters
Issue number8
StatePublished - 13 Aug 2014


  • Helium-Ion Lithography
  • Nano-Optics
  • Plasmonics
  • Third Harmonic Spectroscopy
  • Ultrafast Optics


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