Home » Seminars » Colloquia » Colloquium: December 12, 2012


Colloquium: December 12, 2012


Niek van Hulst*

Antennas for Light

Time: December 12, 2012 Wednesday 16:00
Place: EE01 (Electrical and Electronics Engineering)

Host: Coşkun Kocabaş

ABSTRACT — An optical nano-antenna is the high frequency analogue to the well-known radio-antennas is [1]. Such resonant plasmonic nanostructures allow the control of optical fields at the nanometer scale: super- focussing, local field enhancement, increased radiative rates and angular direction of light emission. The optical antennas have dimensions of typically 20-200 nm, while efficient interaction with active materials (molecules, quantum dots, ..) takes place in the near field, at distances 1 – 10 nm. Clearly nano-control in fabrication and operation is crucial.

First I will address resonant optical nanoantennas positioned at the end of a metal-coated tapered glass fibre near-field probe, thus acting as scanning probes [2]. Direct mapping of the antenna field with single fluorescent beads and molecules reveals a spatial localization of 25-50 nm, demonstrating the importance of such antennas for nanometer resolution optical microscopy [3]. The resonance shows that the antenna is indeed equivalent to its radio frequency dipole analogue.

Next I turn to surface antennas, which are more suitable for large scale fabrication. A quantum dot is placed on the antenna such that it drives the resonance exactly at a point of high mode density. The resulting quantum-dot luminescence is fully emitted in the antenna mode: strongly polarized and with a characteristic Hertz dipole pattern. The directionality emission of the quantum dot is steered by a Yagi-design [4] or even turned into a non-dipolar emission by through multipolar antenna modes.

Finally, antennas are ideal to bring ultrafast photonics to the nanoscale through their support of high-bandwidth excitation, i.e. tuneability [5]. Here, plasmonic antennas are engineered to realize two sought-after applications of ultrafast plasmonics: sub-wavelength phase shaping, and ultrafast hotspot switching. A hotspot switch at sub-100 fs time scale is shown applying only quadratic chirp to the excitation field. This simple, reproducible and scalable approach promises to transform ultrafast plasmonics into a straightforward tool for use in fields as diverse as room temperature quantum optics, nanoscale solid state physics or quantum biology [6].

[1]. Lukas Novotny and Niek F. van Hulst, Antennas for Light. Nature Photonics 5, 83-90 (2011),
[2]. Lars Neumann, Yuanjie Pang, Amel Houyou, Mathieu Juan, Reuven Gordon, Niek F. van Hulst, NanoLetters11, 355-360 (2011)
[3]. T.H. Taminiau, F.D. Stefani, F.B. Segerink, N.F. van Hulst, Nature Photonics, 2, 234 (2008); NanoLetters 7, 28-33 (2007).
[4]. Alberto G. Curto, Giorgio Volpe, Tim H. Taminiau, Mark P. Kreuzer, Romain Quidant, Niek F. van Hulst,Science 329, 930-933 (2010).
[5]. Daan Brinks, Richard Hildner, Fernando D. Stefani and Niek F. van Hulst, Optics Express 19, 26486 (2011).
[6]. Daan Brinks, Fernando D. Stefani, Richard Hildner, Tim H. Taminiau, Niek F. van Hulst, Nature 465, 905-908 (2010).

*ICFO, Barcelona, Spain

The Physics Colloquia are designed to address a non-specialist, broad audience and introduce topics of contemporary research through lectures by leading experts. We warmly invite all members of the student body, including undergraduates enrolled in any programme.

Event Poster

Video recording

Photos from the event