Welcome to the home page of the research group "Ultrafast Nano-Optics" at the Carl von Ossietzky University in Oldenburg
At the international conference „SPIE Photonics West“ a member of our group, Dr. Martin Silies was awarded the "Best Paper Award" within the sub-conference „Advanced Fabrication Technologies for Micro/Nano Optics and Photonics IX“.
The price was donated by Nanoscribe GmbH, a german company specialized on printing three-dimensional structures on the micrometer and sub-micrometer scale.
Within his work, Martin Silies used new lithography technqiues, a combination of Helium and Gallium ion beam milling to fabricate metallic nanostructures with sub-10 nanometer feature size.
He and his colleague want to implement these structures to built an ultrafast plasmonic transistor funded the German Ministry of Science and Education. These transistors are capable of significantly increasing the switching speed compared to conventional electronic transistors.
Im Rahmen dieser Masterarbeit soll die Simulationssoftware "FDTD Solution" von Lumerical eingesetzt werden, um die Wechselwirkung von Licht mit plasmonischen Strukturen zu verstehen und um neuartige, effiziente plasmonische Baulemente zu entwickeln.
Die Stellenausschreibung zu dieser Stelle findest Du hier.
At April, 1st 2015, the Junior Research Group from Martin Silies will start its activity within the Ultrafast Nano-Optics group. The research project will be funded by the Germany Ministry of Science and Technology within the program "NanoMatFutur". Whithin the next four years, Martin Silies and his group members will be working on the interaction of femtosecond light pulses with nanometer-sized, precisely-fabriacted plasmonic nanostructures. Their goal will be the development of an all-optical transistor capable of ultrafast, sub-picosecond switiching.
Very recently, a crew from Beilstein TV was shooting videos about the work in our laboratories. Beilstein TV was founded by the Beilstein Institute and presents short videos about the scientific work of researchers in Germany from all field of research. Here you can find links to the videos that were shot in the last weeks about our research on the interaction of ultrashort light pulses with matter.
Recently, our group demonstrated a new method for the generation of ultrashort electron pulses. On the one hand, it is more efficient than conventional methods, on the other hand it allows a more direct utilization of the electron pulses, because it gives the experimentalist more freedom around the emission site of the electrons.
Our recent work on energy-light conversion in organic solar cells is now shown on the cover of "Laserlab Forum". In the corresponding article from Guilio Cerullo the results of the collaboration with the italian research groups from Cerullo and Elisa Molinari are explained in detail.
December issue of Laserlab Forum
In the last issue of 2014 of "Einblicke", the research magazine of the Carl von Ossietzky University an article is published that shows the work in our laboraties. You can download the article here.
How to squeeze eletric field within an area of a few nanometers has now been shown by our group in a new publication that was very recently published in Nano Letters. The topic is desrcibed here, the publication can be found here.
Photovoltaic cells directly convert sun light into electricity and hence are key technological devices to meet one of the challenges that mankind has to face in this century: a sustainable and clean production of renewable energy. Organic solar cells, using polymeric materials to capture sun light, have particularly favorable properties. They are low-cost, light-weight and flexible, and their color can be adapted by varying the material composition. Such solar cells typically consist of nanostructured blends of conjugated polymers (long chains of carbon atoms), acting as light absorbers, and fullerenes (nanoscale carbon soccer balls), acting as electron acceptors. The primary and most elementary step in the light-to-current conversion process, the light-induced transfer of an electron from the polymer to the fullerene, occurs at such a staggering speed that it has previously proven difficult to follow it directly.
Now, a team of German and Italian researchers from Oldenburg, Modena and Milano reported the first real time movies of the light-to-current conversion process in an organic solar cell. In a report published in the May 30 issue of Science Magazine, the researchers show that the quantum-mechanical, wavelike nature of electrons and their coupling to the nuclei is of fundamental importance for the charge transfer in an organic photovoltaic device.
“Our initial results were actually very surprising”, says Christoph Lienau, a physics professor from the University of Oldenburg who led the research team. “When we used extremely short, femtosecond (1 billionth of a millionth of a second, i.e. 0.000000000000001 seconds) light pulses to illuminate the polymer layer in an organic cell, we found that the light pulses induced oscillatory, vibrational motion of the polymer molecules. Unexpectedly, however, we saw that also the fullerene molecules all started to vibrate synchronously. We could not understand this without assuming that the electronic wave packets excited by the light pulses would coherently oscillate back and forth between the polymer and the fullerene.” All colleagues with whom the scientists discussed these initial results, obtained by PhD student Sarah Falke from Oldenburg in close collaboration with the team of Giulio Cerullo from Politecnico di Milano, leading experts in ultrafast spectroscopy, were skeptical. “In such organic blends, the interface morphology between polymer and fullerene is very complex and the two moieties are not covalently bound”, says Lienau, “therefore one might not expect that vibronic coherence persists even at room temperature. We therefore asked Elisa Molinari and Carlo A. Rozzi, of the Istituto Nanoscienze of CNR and the University of Modena and Reggio Emilia, for help.” A series of sophisticated quantum dynamics simulations, performed by Rozzi and colleagues, provided impressive movies of the evolution of the electronic cloud and of the atomic nuclei in this system, which are responsible of the oscillations found in experiments. “Our calculations indicate”, says Molinari, “that the coupling between electrons and nuclei is of crucial importance for the charge transfer efficiency. Tailoring this coupling by varying the device morphology and composition hence may be important for optimizing device efficiency”.
Will the new results immediately lead to better solar cells? “Such ultrafast spectroscopic studies, and in particular their comparison with advanced theoretical modelling, provide impressive and most direct insight in the fundamental phenomena that initiate the organic photovoltaic process. They turn out to be very similar to the strategies developed by Nature in photosynthesis.”, says Lienau. “Recent studies indicate that quantum coherence apparently plays an important role in that case. Our new result provide evidence for similar phenomena in functional artificial photovoltaic devices: a conceptual advancement which could be used to guide the design of future artificial light-harvesting systems in an attempt to match the yet unrivalled efficiency of natural ones . ”
Link to the article: S. M. Falke et al., Coherent ultrafast charge transfer in an organic photovoltaic blend, Science 344, 1001 (2014), doi: 10.1126/science.1249771
Supplementary Material is available via
For information please contact:
Prof. Dr. Christoph Lienau
Carl von Ossietzky University Oldenburg
Institute of Physics
26129 Oldenburg, Germany
Prof. Dr. Elisa Molinari
Istituto Nanoscienze–Consiglio Nazionale delle Ricerche (CNR),
via Campi 213a
41125 Modena, Italy
Real time quantum simulation of the conversion of light into current in an organic solar cell composed of a polymer chain, and a Fullerene buckyball. The movie lasts for about 100 femtoseconds (fs), and is slowed down by about three hundred thousand billions of times with respect to the real phenomenon, in order to make the ultrafast time scale visible to humans. The quantity depicted illustrates the wavelike oscillations of an electron after light is absorbed at time 0. Each time the upper "bulb" (actually a Fullerene molecule) lights up, a current flows from the bottom to the top of the miniature solar cell. The inset quantifies the amount of charge transfered from the polymer to the Fullerene as a function of time. (Movie: Carlo A. Rozzi).
We have open positions for a Bachelor or a Master student in our group. A description of the scienfitic topic is located here.
Our recent results on the acceleration of electrons are now also published at ProPhysik
and at ingenieur.de
Furhtermore the italian press has noticed this:
The World's smallest electron accelerator
A collaboration of scientists from Oldenburg and Milan uses ultrashort flashes of light to accelerate electrons from single nanoparticles.Light is converted to electricity or to chemical energy – e.g. in solar cells or during photosynthesis in plants – by light rays that drive the electrons into motion. This electronic motion takes place on very small length scales of a few nanometers (a nanometer is one billionth of a meter) and on extremely short time scales of a few femtoseconds (a femtosecond is one billionth part of a millionth of a second).
These activities are highly complex, so that they could not be resolved by even the most sophisticated microscopes. This is why scientists around the world are developing techniques in order to make these processes visible.
Physicists from the University of Oldenburg now reached a breakthrough on this topic. The results from their experiments are now published in the highly respected scientific journal “Nature Photonics”. Within this article, the scientists of the research group "Ultrafast Nano-Optics" of Prof. Dr. Christoph Lienau report how they developed an experimental set-up in order to accelerate electrons from nm-sized gold tips by using ultrashort laser pulses.
„We have developed a sophisticated laser system in collaboration with scientists from Prof. Dr. Giulio Cerullo’s group in Milan, that allows us to generate laser pulses with a precisely defined shape of the electric field“, Dr. Petra Groß explains, who supervises the experiments in Oldenburg. “With these so called phase-controlled laser pulses we are able emit electrons from a few nanometer-sized gold tip and to accelerate them in a precise manner to a distinct direction determined by the light field” she adds.
This is similar to the way experienced golfers can control the flight path of the golf ball by their drive. However, the acceleration within these experiments is much stronger: While the golf ball is accelerated with up to one hundred times earth’s gravity, the acceleration experienced by the electrons in the laboratory is 20 orders of magnitude larger than gravity. The electrons then have velocities of about one percent of the speed of light.
“The gold tips are important for us, since they act as a well-defined starting point for their electrons. The tips are simply designed, so that the experimental results can be well explained by model simulations. “We can therefore learn a lot about how electrons act on extremely short temporal and extremely short spatial scales” Lienau concludes. This knowledge is of central interest for understanding the complex motion of electrons in components like solar cells. The scientists in Oldenburg therefore work hard in order to develop new scientific techniques for the investigation of energy conversion in solar cells and biological nanostructures.
The article is published in Nature Photonics doi.10.1039/nphoton.2013.288
The image shows the energy distribution of electrons that are emitted by laser pulses from a gold tip.
Sarah Falke awarded by "green photonics" for her PhD thesis
Sarah Maria Falke from the "Ultrafast Nano-Optics" has been awarded for her PhD thesis the young academics prize "Green Photonics" of the German Engineering Comunity VDI at the Hanover fair. Within her thesis Ms. Falke investigated the energy conversion of light to current in organic solar cells on a femtosecond time scale. A link to the Green Photonics can be found here and here.
Experimental results on ultrafast rabi-oscillations published in "nature photonics"
Today experimental results about the observation of ultrafast coherent Rabi oscillations have been published in Nature Photonics. The observed coupling between excitons and surface plasmon polaritons that takes place on a femtosecond time scale can be seen as an important step towards optical computers. A link to the published work can be found at Publications.
At the 08.02.2013 Christoph Lienau talked about this topic in the science radio show "Logo" on NDR Info. The link to the podcast of the show can be found here, a recording of the talk can be found here (in german).
Publication on the generation of Femtosecond electron pulses in "Physical Review Letters"
Our group was now able to publish experimental resulsts about the generation of ultrashort electron pulses in the latest issue of "Phyiscal Review Letters". In this work, the trajectories of electrons that have been emitted from a nm-sized gold tip using ultrashort laser pulses have been both investigated experimentally and theoretically. Therefore the underlying physical processes could be determined. A link to this publicatiuon can be found at Publications.
left: Björn Piglosiewicz is aligning the laser system, that generates ultrashort electron pulses. right: Prof. Dr. Christoph Lienau supervised the project.
Work about the localization of light published in "Nature Photonics".
At the 16th of April 2012 an article from our group was published in Nature Photonics about the localization of light. Herein we describe, how it was possible to investigate the storage (localization) of light in disordered, dielectric media both spatially and time-resolved. A link to the paper is found at Publications.
Manfred Mascheck in the lab, in which the localization of light has been invesigated.
The Ultrafast Nano-Optics group, from left to right: Sai Kiran Rajendran (guest from Prof. Cerullos group [Milano]), Simon Becker, Manfred Mascheck, Bernd Schwenker, Margret Warns, Ephraim Sommer, Heiko Kollmann, Jens Brauer, Martin Esmann, Petra Groß, Christoph Lienau, Wei Wang, Jan Vogelsang, Antonietta deSio, Ralf Vogelgesang, Slawa Schmidt, Björn Piglosiewicz, Martin Silies (missing: Melanie Lammers, Sarah Falke, Pascal Engelke, Stephan Streit, Raimond Angermann)
3/20/2009 - Article on our research activities in "Neues Deutschland"
The nationwide newspaper "Neues Deutschland" published an article (in German) about our studies on the interaction of light and electrons in nanostructures.
2/23/2009 - New review article just appeared in Laser and Photonics Reviews
Parinda Vasa and Robert Pomraenke have just published a comprehensive review article in Laser and Photonics Reviews together with Claus Ropers from the University of Göttingen. The article covers various research topics in "Ultrafast Nano-Optics" which are currently being pursued in our group.
Examples include measurements of the ultrafast nonlinear response of single semiconductor quantum dots, the generation of novel nanoscopic electron source and work on exploring the unusual effects that occur when metallic and metal-semiconductor hybrid nanostructures interact with light.
Please have a look!
9/19/2008 - New paper
"Coherent Exciton-Surface-Plasmon-Polariton Interaction in Hybrid Metal-Semiconductor Nanostructures" by Vasa et al., published in Phys. Rev. Lett.
Report in Physical Review Focus about the PRL by Vasa et al.