ATTOSECOND SCIENCE NETWORKS ‘ESSENTIAL’
Europe has traditionally been very strong in the fi eld of attosecond science, due in part to effective collaboration between researchers in different countries. ‘Since 2000 the European Union has funded several collaborative networks to promote attosecond science,’ says Marc Vrakking, director of the attosecond science division at the Max-Born Institute in Berlin, Germany and coordinator of ATTOFEL. ‘The latest network is ATTOFEL, a training network for early-stage researchers.’ Vrakking believes networks like this are
essential if Europe wants to maintain its lead in this fi eld of science and train the scientists who will make large-scale facilities like ELI-ALPS a success. And the collaborative approach is already bearing fruit, with several breakthroughs already reported. He highlights a paper in the journal Nature, which involved a large collaboration between many of the ATTOFEL members. ‘We reported the fi rst application of attosecond pump-probe spectroscopy to molecular science.’ An attosecond pulse was used to ionise
a hydrogen molecule and the localisation of the electronic charge distribution within the molecule was measured with attosecond time resolution by varying the delay between the
➤
ALPS will have a huge impact not only on physics, biology, medicine and chemistry, but also on the laser industry.
‘The technical challenges that will have to be tackled on a short timescale will drive forward technology in a number of areas faster than might happen otherwise,’ says Tisch. ‘For example, there is the development of the high-power, high-repetition rate pump-lasers required for the parametric amplifi er in the laser chain, which will require close cooperation with industry.’ Veisz agrees, but points out that while industry cooperation is needed to develop pump laser systems, ELI-ALPS will also drive development of a new class of lasers. ELI-ALPS’s lasers will be based on optical parametric chirped- pulse amplifi cation (OPCPA), a relatively new amplifi cation technique that results in more compact and simpler lasers. An OPCPA system requires fewer amplifi cation stages than a conventional laser, often requiring just one pass due to the higher amplifi cation. This eliminates the need for complicated multipass geometries and means lasers can be built in a much simpler way. Thermal effects in the amplifi er crystal, such as thermal lensing, are much weaker than in a laser amplifi er, since there is only a small amount of heating due to weak parasitic absorption. This, together with the very high quantum effi ciency, allows for scaling to very high energy and peak power levels, and also to a high beam quality of the amplifi ed pulses. ‘I believe this will have a major impact on the
Artist impression of the localisation of an electron in a dissociating h2
+ molecule. hills and
valleys represent localisation of the electron on, respectively, the left and the right proton, with time advancing from left to right in the diagram. Courtesy of Thorsten Naeser, MPQ-Garching
pump and probe pulses. ‘We were able to visualise the interactions between electrons and also the interactions between electrons and the atomic nuclei,’ says Vrakking. ‘We are now looking at using this powerful technique on more complex molecules.’
www.attofel.eu
European laser industry,’ says Veisz. This is just one of the ways in which ELI- ALPS will impact European science. Physicists, chemists and engineers are all waiting to see what will happen. While it is hard to predict what the attosecond landscape will be like in fi ve years’ time when ELI-ALPS commences operation, it is clear that we are entering into a new era in our understanding of atomic and molecular physics. Until then, all eyes are on Szeged, where ELI-
ALPS coordinators meet this month to discuss the details of this unique facility, which, it is hoped, will make many dreams come true. l
For further information
the number of groups conducting attosecond research in europe is continuously growing. here is a selection of links for the groups mentioned in this article and other groups considered leaders in this fi eld.
AMolF –
www.amolf.nl Attosecond technology –
www.attosecond.org eth Zurich –
www.ulp.ethz.ch
Foundation for research and technology – hellas –
www.iesl.forth.gr
laboratoire d’optique Appliquee –
http://loa.ensta.fr lund University –
www.atto.fysik.lth.se
Max planck institute for Quantum optics –
www.attoworld.de Max-Born institute –
www.mbi-berlin.de politecnico di Milano –
www.fi si.polimi.it
www.electrooptics.com
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