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
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences