8 March 2013

COBRA COLLOQUIUM: Friday March 8, 2013 at 15:00 – 16:00 in Auditorium room 10 !!!!

Speaker: Prof. dr. Niek F. van Hulst

Title: Antennas for Light

Abstract: An optical nano-antenna is the high frequency analogue to the well-known radio-antennas*. Such resonant plasmonic nanostructures allow the control of optical fields at the nanometer scale: super- focusing, 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 fiber near-field probe, thus acting as scanning probes. 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. 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 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. 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.

* Lukas Novotny and Niek F. van Hulst, Antennas for Light. Nature Photonics 5, 83-90 (2011)

Biography: Niek van Hulst studied Astronomy & Physics, and obtained his PhD in Molecular & Laser-Physics at the University of Nijmegen (1986), on microwave-laser double resonance molecular-beam spectroscopy. After research in non-linear optics of organic materials, integrated optics, atomic force and near-field optical microscopy, in 1997 he became Professor in Applied Optics at MESA+ Institute for NanoTechnology, University of Twente, with focus on single molecule detection, scanning probe technology and applications in molecular biology and chemistry. In 2005, attracted by the Catalan innovative science policy, he started as ICREA Research Professor and senior group leader at ICFO – the Institute of Photonic Sciences, in Barcelona. He is coordinator of the Spanish CONSOLIDER program NanoLight.es; Recipient ERC Advanced Grant; 2010 Barcelona Prize for Scientific Investigation; 2003 European Science Award; Fellow OSA.

After the colloquium (around 16:00) we organize a mini-colloquium in which three COBRA researchers, one from each of the three COBRA groups, will give a short presentation about his or her work.

For the Electro Optical Communication Group:
Speaker: Prometheus Dasmahaptra Title: Broadband switching using higher order resonators
For the Photonic Integration Group:
Speaker: Yuqing Jiao Title: Towards a monolithically integrated OCT system
For the Photonics and Semiconductor Nanophysics Group:
Speaker: Juanita Bocquel Title: Shape Control in GaAs/AlGaAs Droplet Epitaxy Quantum Dots

The audience is invited to an informal gathering following the colloquium in the canteen of the Auditorium, section D.

The next COBRA Colloquium will take place on Friday, April 12, 2013 
Location: TU/e, the Film Theater of Grand Café and Film house De Zwarte Doos
Time: 15:00 hours