Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecular nanoprobe for nanoantenna optical near-fields

29.07.2013
Researchers at the University of Stuttgart measure for the first time near-fields of three-dimensional optical nanoantennas.

Researchers at the University of Stuttgart measured for the first time optical near-field intensities of three-dimensional nanoantennas. The team of Prof. Harald Giessen at the 4th Physics Institute achieved those results with a novel scheme of nanospectroscopy and published their paper in the journal “Nature Communications”.*)


Molecules (blue) are positioned with nanometer accuracy next to three-dimensional optical nanoantennas. Vibrations in the molecules are excited. The oscillation strength depends on the near-field distribution (red) and can be measured in the far-field.

(University of Stuttgart)

Their method gives new insight into light-matter coupling at the nanoscale and allows precise measurement of enhanced optical near-field intensities generated by optical antennas. This technique can facilitate the engineering of future sensing platforms with extremely high sensitivity.

Molecules exhibit vibrational resonances in the mid-infrared and terahertz regions which is called the molecular fingerprint since it is unique for each substance. With far-field spectroscopy techniques, molecules can be detected and unambiguously identified. Nevertheless, huge quantities of molecules are needed since the excitation of the vibrational resonances is very inefficient. Metallic optical nanoantennas are resonant to incident radiation and generate high near-fields in their direct vicinity. These intensive fields can be used to make small amounts of molecules or even single molecules visible. This plays an important role in early disease diagnostics and in the detection of harmful substances or explosive gas mixtures, such as hydrogen in air.

The Stuttgart group was able to position a few molecules next to gold nanoantennas. Using electron-beam lithography they achieved an accuracy as small as a few nanometers. Due to the high near-field intensities the excitation of the molecular vibrations was orders of magnitude more efficient and was measurable with far-field spectroscopy techniques. By positioning the molecules at different locations with respect to the optical gold nanoantenna the underlying physical process of the vibrational excitation was identified for the first time. In particular, the team of researchers found that the efficiency of the vibrational excitation scales linearly with the near-field intensity generated by the optical antennas.

With this insight the researchers developed a new method to measure quantitatively near-field intensities of optical nanoantennas. The resolution limit of conventional microscopy was overcome since the detection volume using the molecules was much smaller than the wavelength cubed. Compared to state-of-the-art optical near-field microscopy, the method of the Stuttgart group exhibits the unique advantage of measuring near-field distributions of three-dimensional nanoantenna structures. Daniel Dregely was able to incorporate molecules at specific locations during the fabrication process of the antenna structure. He could then detect the vibrational excitation and thus measure the near-field intensity. Such complex nanostructures add another degree of freedom to enhance the interaction of light with single molecules at the nanoscale. The design of future sensing devices will benefit from this new tool of assessing near-field intensities of three-dimensional optical antennas.

*) Reference: D. Dregely, F. Neubrech, H. Duan, R. Vogelgesang, and H. Giessen, “Vibrational near-field mapping of planar and buried three-dimensional plasmonic nanostructures”, Nature Communications (2013). http://www.nature.com/naturecommunications

Contact:
Prof. Harald Giessen, University of Stuttgart, 4th Physics Institute,
Tel. +49 711 68565111, e-mail: giessen (at) physik.uni-stuttgart.de
or
Dipl.-Phys. Daniel Dregely, University of Stuttgart, 4th Physics Institute, Tel. +49 711 68564961, e-mail: d.dregely (at) physik.uni-stuttgart.de

Andrea Mayer-Grenu | idw
Further information:
http://www.uni-stuttgart.de
http://www.nature.com/naturecommunications

More articles from Physics and Astronomy:

nachricht Ultra-compact phase modulators based on graphene plasmons
27.06.2017 | ICFO-The Institute of Photonic Sciences

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>