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 New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society

nachricht NASA's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Link Discovered between Immune System, Brain Structure and Memory

26.04.2017 | Life Sciences

New survey hints at exotic origin for the Cold Spot

26.04.2017 | Physics and Astronomy

NASA examines newly formed Tropical Depression 3W in 3-D

26.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>