Recent innovations in laser technology have provided radiation sources for attosecond (10 to the power of -18 sec) light flashes that can freeze the ultrafast motion of electrons inside atoms and molecules.
The range of possible applications is however limited by the low flux of the current attosecond sources. In a proof of principle experiment a team of MPQ scientists (Attosecond and High-Field Physics Division, Prof. Ferenc Krausz) has now demonstrated a novel way of generating attosecond light flashes with unprecedented intensity. The article by Y. Nomura et al., (Nature Physics, Advance Online Publication December 14, 2008, DOI 10.1038) confirms that relativistically driven overdense plasmas are able to convert infrared laser light into harmonic XUV radiation with high efficiency.
Furthermore it demonstrates the feasibility of confining unprecedented amounts of light energy to within less than one femtosecond. The long term goal - reaching sub-atomic resolution simultaneously in space and time - will have far-reaching impact, from physics and chemistry through biology and medicine to future information technologies.
State of the art technique for producing ultrashort coherent light pulses in the XUV spectral range is the method of generating "harmonics" by converting laser light travelling through a gas target to radiation whose frequency is an integer times the frequency of the fundamental oscillation. By contrast the scientists focus short laser pulses from the Titanium-Sapphire-Laser ATLAS (IR, 800 nm) onto a solid target creating an overdense plasma on its surface in which the electrons oscillate in the strong laser field with velocities close to the speed of light. Here two mechanisms give rise to harmonic generation. On the one hand the electrons reflect the incoming laser light causing (depending on their direction) a Doppler shift towards higher frequencies. On the other hand - and this process is the dominant one in this work - the electrons that are injected into the surface excite plasma waves in their wake. Under certain conditions these are converted to electromagnetic radiation at higher harmonics of the driver frequency. A spectral filter suppresses residual IR-light and selects a range of harmonics.
"There is no way to measure the time structure of the sequence of out coming attosecond flashes directly", says Dr. George Tsakiris, leader of the project. "We therefore have to resume to a trick: we let two replica of the attosecond pulse train interact with a Helium gas jet. By varying the time delay between them and recording the corresponding number of resulting Helium ions we can deduce the temporal structure of the XUV radiation." "We have demonstrated for the first time that the harmonics from solid targets are indeed emitted as a train of attosecond pulses", adds Rainer Hörlein, PhD student at the experiment.
More generally spoken the physicists have demonstrated the first alternative method to the generation of harmonics from noble gases for the production of attosecond pulses. In addition the pulses are orders of magnitude more intense than those generated with conventional methods. Unlike gas-harmonics the new method is expected to be highly scalable and to exhibit no limitation on the usable laser intensity: the higher the laser intensity the shorter and more energetic the attosecond pulses should be. Much more intense attosecond pulses will significantly increase the scope of possible experiments with attosecond resolution and will make pump-probe experiments with attosecond pulses feasible. [O.M.]
Dr. Olivia Meyer-Streng | Max-Planck-Gesellschaft
Further reports about: > Attosecond > Attosecond flashes > DOI > Max Planck Institute > Physic > Quantum > UV radiation > XUV > attosecond pulses > electrons > harmonic XUV radiation > infrared laser light > laser light > laser technology > pump-probe experiments > solid-density relativistic plasmas
NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center
Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Trade Fair News
28.03.2017 | Life Sciences
28.03.2017 | Information Technology