1 research outputs found
Toward Plasmonics with Nanometer Precision: Nonlinear Optics of Helium-Ion Milled Gold Nanoantennas
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<sup>+</sup>-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<sup>+</sup>-FIB and milling-based He<sup>+</sup>-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<sup>+</sup>-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