research — Laser physicists from the Ludwig-Maximilians-Universität Munich and the Max Planck Institute of Quantum Optics in collaboration with colleagues from the United States and Japan, have taken snapshots of carbon molecules C60, showing how they transform in intense infrared light.

research — Physicists at the Max Planck Institute for Quantum Optics, the Ludwig-Maximilian University in Munich and Umeå University have, for the first time, made use of plasmas consisting of relativistic electrons to generate isolated and highly intense attosecond laser pulses.

research — Researchers at the TU Munich, the Max Planck Institute of Quantum Optics and the TU of Vienna have succeeded in measuring the precise duration of the photoelectric response.

research — Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of health. Researchers at the Laboratory for Attosecond Physics (LAP) – a joint venture between Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ) in Garching near Munich – want to use brilliant infrared light to study molecular disease markers in much greater detail, for example to facilitate early stage cancer diagnosis. The team has developed a powerful femtosecond light source which emits at wavelengths between 1.6 and 10.2 micrometers. This instrument should make it possible to detect organic molecules present in extremely low concentrations in blood or aspirated air.

research — Researchers from Ludwig-Maximilians-Universität (LMU), the Max Planck Institute of Quantum Optics (MPQ) and the Technical University of Munich (TUM) have taken a major step towards the clinical application of a new laser-based source of X-rays. They recently demonstrated that the instrument enables the tomographic reconstruction of the three-dimensional fine structure of a bone sample within a few minutes. Up to now, laser-based measurements of this sort took several hours. The breakthrough was made possible by the further development of ATLAS, the high-performance laser in LMU’s Laboratory for Extreme Photonics (LEX Photonics) der LMU on the Research Campus in Garching. Reconstruction of the sample from the imaging data was also facilitated by the use of specially designed computer programmes.

research — Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort light pulses in the infrared and visible regions of the spectrum. Extremely high-energy laser pulses, each lasting for a few femtoseconds, have made spectacular experiments possible, which have in turn yielded revolutionary insights. Above all, the growth in understanding of the interaction between light and electrons opens up entirely new prospects for the future of electronics. In the journal Review of Modern Physics (10 April 2018), Dr. Stanislav Kruchinin, Prof. Ferenc Krausz and Dr. Vladislav Yakovlev from the Laboratory for Attosecond Physics (which is jointly run by Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ)) in Munich, provide a timely overview of current research in ultrafast solid-state physics. They describe recent breakthroughs and take a look at what we can expect from the field in the coming years.

research — In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very bright, and the photons delivered must have sufficiently high energy. This combination of properties has been sought in laboratories around the world for the past 15 years. Physicists at the Laboratory for Attosecond Physics (LAP), a joint venture between the Ludwig-Maximilians-Universität Munich (LMU) and the Max Planck Institute of Quantum Optics (MPQ), have now succeeded in meeting the conditions necessary to achieve this goal. In their latest experiments, they have been able to observe the non-linear interaction of an attosecond pulse with electrons in one of the inner orbital shells around the atomic nucleus. In this context, the term ‘non-linear’ indicates that the interaction involves more than one photon (in this particular case two are involved). This breakthrough was made possible by the development of a novel source of attosecond pulses. One attosecond lasts for exactly one billionth of a billionth of a second.

research — Infrared light has a keen sense for molecules. With the help of this light, researchers are able to go in search of the small particles which shape and determine our lives. The phenomenon, in which infrared light sets molecules in vibration, is pivotal in this search. Scientists are exploiting this phenomenon by using infrared light to analyze the molecular makeup of samples. In the hope that this analysis can become even more exact, the laser physicists from the Laboratory of Attosecond Physics (LAP) at the Ludwig-MaximiliansUniversität(LMU) Munich and the Max Planck Institute of Quantum Optics (MPQ) have developed an infrared light source that has an enormously broad spectrum of wavelengths. This light source is the first of its kind worldwide and can be used to help detect the smallest amounts of molecules in liquids like blood.

research — Many chemical processes run so fast that they are only roughly understood. To clarify these processes, a team from the Technical University of Munich (TUM) has now developed a methodology with a resolution of quintillionths of a second. The new technology stands to help better understand processes like photosynthesis and develop faster computer chips.

research — In their experiments, the group fired a powerful laser pulse at a micrometer-sized plastic sphere, blasting a bunch of protons from the target and accelerating them to velocities approaching the speed of light. The resulting velocity distribution is much narrower than that obtained when thin metal foils are used as targets.

research — The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a billionth of a second). What exactly happens in such an astonishingly short time has so far remained largely inaccessible. Now a research team led by Dr. Peter Baum and Dr. Yuya Morimoto at the Laboratory for Attosecond Physics (LAP), a collaborative venture between LMU Munich and the Max Planck Institute of Quantum Optics (MPQ), has developed a new mode of electron microscopy, which enables one to observe this fundamental interaction in real time and real space.

research — When metal clusters, small nanoparticles consisting of just a few thousand atoms, are exposed to intense laser light, electrons inside the particle are excited to a swinging collective motion. The electron cloud’s motion, a plasmon, can be excited resonantly with light of a suitable color leading to very high amplitudes and an enhanced electric field inside the cluster. In the experiment, which was conducted at the Institute of Physics in Rostock, a team of researches around Prof. Thomas Fennel has now deliberately exploited this enhanced near-field. With so-called two-color laser pulses the scientists tailored the plasmonic field via the waveform of the light field. This led to a controlled slingshot-type acceleration of electrons traversing the nanoparticle within only one optical cycle. These experimental results, together with their interpretation by a theoretical model, were now published in the Journal Nature Communications.

research — When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole behind. For a long time, scientists have suspected that the liberated electron and the positively charged hole form a new kind of quasiparticle — known as ‘core-exciton’. But so far, there has not yet been a real proof of its existence. Scientists have a wide range of tools to track excitons in semiconductors in real-time. Those are generated by ordinary light, and can be employed in various applications in optoelectronics and microelectronics. On the contrary, core-excitons are extremely short-lived, and up to now, no technique was available to track their motion and deduce their properties.

research — The Federal Ministry of Education and Research (BMBF) has called for the implementation of a new network of excellence under the lead of the Fraunhofer Institute of Applied Optics and Precision Engineering (IOF). The Max Planck School of Photonics (MPSP) focusses the key strengths of the German Photonics Community and will support highly skilled young researchers on a world class level. The national network of excellence aims to level the playing field with elite institutions, such as the American Havard University or the Massachusetts Institute of Technology (MIT) by setting new standards in the research with light.

research — We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence relatively still in a dielectric crystal lattice. This idyll has now been heavily shaken up by a team of physicists from various research institutions, including the Laboratory of Attosecond Physics (LAP) at the Ludwig-Maximillian’s-Universität Munich (LMU) and the Max Planck Institute of Quantum Optics (MPQ), the Institute of Photonics and Nanotechnologies (IFN-CNR) in Milan, the Institute of Physics at the University of Rostock, the Max Born Institute (MBI) in Berlin, the Center for Free-Electron Laser Science (CFEL) in Hamburg and the University of Hamburg. For the first time, these researchers managed to directly observe the interaction of light and electrons in a dielectric, a non-conducting material, on timescales of attoseconds (billionths of a billionth of a second).

research — Modern electronics and digital technologies rely on the control of electric current in semiconductor devices, from computers to smartphones and amplifiers. An international study by scientists from Monash University (Melbourne, Australia) and the Max Planck Institute of Quantum Optics (Garching, Germany) lays foundations for a dramatic performance increase of semiconductor-based signal-processing technologies.

research — When light strikes electrons in atoms, their state can change unimaginably quickly. The laser physicists at Ludwig-Maximilians-Universität Munich (LMU), the Technische Universität München (TUM) and the Max Planck Institute of Quantum Optics (MPQ) have measured such a phenomenon – namely that of photoionization, in which an electron exits a helium atom after excitation by light – for the first time with zeptosecond precision. A zeptosecond is a trillionth of a billionth of a of a second (10\(^{21}\) seconds). This is the greatest accuracy of time determination of an event in the microcosm ever achieved, as well as the first absolute determination of the timescale of photoionization.

research — The performance of modern electronic devices such as computers or mobile phones is dictated by the speed at which electric currents can be made to oscillate inside their electronic circuits. The shrinkage of basic electronic elements, such as transistors, to smaller and smaller dimensions over the last decades has allowed the development of ever-faster electronic devices like the ones used in everyday life. However, this methodology of speeding up electronics is now rapidly approaching its ultimate limits; devices are becoming nearly as small as only a few atoms (!) and conventional principles of electronic technology hardly apply in these dimensions, calling for new routes to be discovered.

research — Light, when strongly concentrated, develops an enormous power. Using this concentrated energy, a team of physicists from the Institute of Experimental Physics – Medical Physics at the cluster of excellence the Munich-Centre for Advanced Photonics (MAP) of Ludwig-Maximilians-Universität München caused an explosion. The researchers concentrate laser light onto beads of plastic just a few micrometers in size. The concentrated energy blows up the nanoparticles. This releases radiation made up of positively charged atoms (protons). Such proton beams could be used in future for treating tumors, and in advanced imaging techniques.

research — Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and it is difficult to capture them in action. However, a better understanding of the dynamics of field variation in electronic components, such as transistors, is indispensable for future advances in electronics. Researchers in the Laboratory for Attosecond Physics (LAP), jointly run by Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ), have now taken an important step towards this goal – by building an electron microscope that can image high-frequency electromagnetic fields and trace their ultrafast dynamics.

research — The interaction between light and matter is of key importance in nature, the most prominent example being photosynthesis. Light-matter interactions have also been used extensively in technology, and will continue to be important in electronics of the future. A technology that could transfer and save data encoded on light waves would be 100.000-times faster than current systems. A light-matter interaction which could pave the way to such light-driven electronics has been investigated by scientists from the Laboratory for Attosecond Physics (LAP) at the Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ), in collaboration with colleagues from the Chair for Laser Physics at the Friedrich-Alexander-Universität Erlangen-Nürnberg. The researchers sent intense laser pulses onto a tiny nanowire made of gold. The ultrashort laser pulses excited vibrations of the freely moving electrons in the metal. This resulted in electromagnetic ‘near-fields’ at the surface of the wire. The near-fields oscillated with a shift of a few hundred attoseconds with respect to the exciting laser field (one attosecond is a billionth of a billionth of a second). This shift was measured using attosecond light pulses which the scientists subsequently sent onto the nanowire.

research — Light waves might be able to drive future transistors. The electromagnetic waves of light oscillate approximately one million times in a billionth of a second, hence with petahertz frequencies. In principle also future electronics could reach this speed and become 100.000 times faster than current digital electronics. This requires a better understanding of the sub- atomic electron motion induced by the ultrafast electric field of light. Now a team of the Laboratory for Attosecond Physics (LAP) at the Max-Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität (LMU) and theorists from the University of Tsukuba combined novel experimental and theoretical techniques which provide direct access to this motion for the first time.

research — Investigating light-matter interaction beyond the applicability of the conventional nonlinear optics, we challenged the assumption that light-field control requires the laser frequency to be far from any resonant transitions. Specifically, we studied the interplay between intraband electron motion and Rabi oscillations. In the case where the central frequency of a laser pulse was close to the band gap of GaAs, we observed a new kind of nonlinear resonance: “kicked anharmonic Rabi oscillations” (KARO). In this regime, interband transitions mainly take place when electrons pass near the Brillouin zone center. Interference between such kick-like transitions leads to residual population distributions that are strongly asymmetric in reciprocal space. Consequently, in this regime, a laser pulse efficiently induces a residual electric current that is controlled by the carrier-envelope phase of the pulse.

research — Using ultrashort laser pulses an international team at the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität Munich has managed to manipulate the positions of atoms in hydrocarbon molecules.
Light can conduct the play of atoms and molecules in the microcosm. Humans manage to interfere with this play. Researchers from the Laboratory for Attosecond Physics (LAP) of the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität (LMU) and from the Department of Chemistry at the LMU have now used light to reconfigure hydrocarbons. Using ultrashort laser pulses they removed an outer hydrogen atom from one side of a hydrocarbon molecule and directed it to the opposite side, where it reattached. The method could be used in the future to synthesize new substances by controlling chemical reactions.

research — Seeing how atoms and electrons in a material respond to external stimuli can give scientists insight into mysteries of solid-state physics, like how high temperature superconductors and other exotic materials work. Short pulses of electrons can be used to film such motions. When an electron scatters from a crystal, due to its quantum mechanical wave-like properties, it interferes with itself to create a diffraction pattern. By recording these patterns, researchers can see the atomic and electronic structure of the material, resolving details smaller than the size of an atom. Short electron pulses are, however, difficult to generate, because electrons carry a charge and move slower than the speed of light. In particular, electron pulse technology is still far away from the time resolution required to see the motions of electrons inside a material. Now, a team headed by Dr. Peter Baum and Prof. Ferenc Krausz from the Laboratory for Attosecond Physics (LAP), the Ludwig-Maximilians University (LMU) and the Max- Planck Institute of Quantum Optics (MPQ) has succeeded in developing a new technique for controlling ultrafast electron pulses (see: ‘Movies out of the Microcosm’). While, to date, microwave technology has been used to control electron pulses, the LMU and MPQ researchers have for the first time used optically-generated terahertz radiation. Using the new technique, the physicists have succeeded in significantly shortening electron pulses. This terahertz method offers the potential of visualizing not only atoms but also electrons in motion.

research — In the race to establish ever-faster electronics, light could play an important role. For instance, using light pulses of a precisely controlled waveform, physicists aim to switch electric currents in electronics circuits with light frequencies. But will electrons in such circuits follow light oscillations instantaneously? How fast will electrons react to the push of a “light-based” button? Or, from a more fundamental perspective: how fast do electrons bound in atoms, molecules or solids respond to light? Now, an international collaboration of physicists led by Dr. Eleftherios Goulielmakis, head of the research group “Attoelectronics” at the Max Planck Institute of Quantum Optics, researchers from Texas A&M University, USA, and the Lomonosov Moscow State University, " have been able to track the effect of this delay for the first time". By creating the first optical attosecond pulse and using it to set electrons in krypton atoms in motion, they discovered that it takes as long as 100 attoseconds for electrons to respond to the electromagnetic forces of light.

research — Those who want to explore the microcosm need exact control over laser light. Only with its help is it possible to explore electron motion and to influence their behavior. Now, scientists at the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität Munich (LMU) have developed a measuring system that is able to determine laser pulses with a wide bandwidth in the infrared spectrum of light precisely. In the infrared wavelength range as short as 1200 nanometers this was only possible with the help of complex vacuum systems until now. The new system can be used for the precise generation of attosecond-duration light bursts for the exploration of atomic systems, as well as for the controlled dynamics of electrons in crystals.

research — Electrons are odd particles: they have both wave and particle properties. Electron microscopy has been taking advantage of this phenomenon for roughly a century now and grants us a direct insight into the fundamental components of matter: molecules and atoms. For a long time, still images were provided, but for some years now scientists are making tremendous progress in short-pulse technology. They create beams of electron pulses, which can, due to their extremely short flashing, provide us with very sharp images of moving atoms and electrons. Nevertheless, some of the fastest processes still remained blurred. A team of the Laboratory for Attosecond Physics (LAP) from the Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ) has now managed to shorten electron pulses down to 28 femtoseconds in duration. One femtosecond is a millionth of a billionth of a second (10-15 s). Such shutter speeds enable us to directly observe the truly fundamental motions of atoms and molecules in solids, similar to stroboscopy.

research — Electrons hit by strong laser pulses change their location on ultrashort timescales, i.e. within a couple of attoseconds (1 as = 10\(^{18}\)sec). In cooperation with the Center for Nano-Optics of Georgia State University in Atlanta (USA), scientists at the Laboratory for Attosecond Physics (LAP) of the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität (LMU) have made simulations of processes that take place when electrons in a layer of carbon atoms interact with strong laser light. The purpose of these simulations is to gain insight into light-matter-interactions in the microcosm. A better understanding of the underlying physical processes could lead to light-wave driven electronics that would operate at light frequencies, which is a hundred thousand times faster than state-of-the-art technologies. Graphene with its exceptional properties is considered to be very well suited as an example system for prototype experiments.

research — Scientists often need to detect and measure levels of specific substances in a sea of irrelevant molecules, and infrared light offers an ideal tool for this task. Infrared radiation is invisible to the human eye, but molecules react with mid-infrared light in ways that are extremely sensitive to their precise atomic structure. This provides a means of identifying with great specificity molecular solutes present in very low concentrations. Lasers that generate light in the mid-infrared range suitable for use in molecular sensors are therefore the subject of intensive research. Now teams from the Ludwig-Maximilians-Universität (LMU) and the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics (MPQ), in collaboration with the Institute of Photonic Sciences (ICFO) in Barcelona, have developed a unique source of coherent radiation for this purpose.

research — With laser light, physicists in Munich have built a miniature X-ray source. In so doing, the researchers from the Laboratory for Attosecond Physics of the Max Planck Institute of Quantum Optics and the Technische Universität München (TUM) captured three-dimensional images of ultrafine structures in the body of a living organism for the first time with the help of laser-generated X-rays. Using light-generated radiation combined with phase-contrast X-ray tomography, the scientists visualized ultrafine details of a fly measuring just a few millimeters. Until now, such radiation could only be produced in expensive ring accelerators measuring several kilometers in diameter. By contrast, the laser-driven system in combination with phase-contrast X-ray tomography only requires a university laboratory to view soft tissues. The new imaging method could make future medical applications more cost-effective and space-efficient than is possible with today’s technologies.

research — The relationship between strong laser pulses and glass nanoparticles is a special one – one that could influence medical methods, as scientists from Rostock, Munich, and Berlin have discovered. The interplay between light and matter was studied by a team of physicists and chemists from the Laboratory for Attosecond Physics (LAP) at the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität Munich (LMU), from the Institute of Physics of the University of Rostock, and from the Freie Universität Berlin. The researchers studied the interaction between strong laser pulses and glass nanoparticles, which consist of multiple millions of atoms. Depending on how many atoms were contained in the nanoparticles, these objects reacted differently over attosecond timescales (an attosecond is a billionth of a billionth of a second). Depending on their size, so called nearfields (electromagnetic fields close to the particle surface) were induced by the laser pulses, resulting in a controlled directional emission of electrons. These findings could eventually extend cancer therapy and imaging methods in medicine. The study was published in the latest issue of the journal Nature Communications.

research — The interaction of high-intensity laser light with solid targets could someday serve as the basis of table-top sources of high-energy ions for medical applications. An international team led by physicists of the LMU affiliated with the Munich-Centre for Advanced Photonics (MAP), a Cluster of Excellence based in Munich, and in cooperation with scientists from the Max Planck Institute of Quantum Optics, has taken another step towards this goal. They have done so by boosting the efficiency of a technique that uses extremely intense pulses of laser light to eject packets of high-energy ions from diamond-like carbon foils. In their experiment, the researchers coated one side of the foil with carbon nanotubes. Upon laser irradiation, the layer acts like a lens to focus and concentrate the light energy on the foil, which results in the production of much more energetic ion beams. This makes experiments with high-energy carbon ions on cells feasible for the first time, and brings light-driven generation of ionizing radiation closer to practical application.

research — For over a century, medical imaging has made use of X-rays produced in a specialized type of vacuum tube. The major disadvantage of this method lies in the poor quality of the emitted radiation. The source emits radiation from a large spot into all directions and over a broad energy range. These features are responsible for the relatively modest resolution attainable with this mode of imaging. X-rays generated in synchrotrons provide much higher resolution, but their dimensions and cost preclude their routine use in clinical settings. However, an alternative approach is now available, for two laser pulses can generate X-rays of similar quality to synchrotron radiation in devices with a far smaller footprint: One pulse accelerates electrons to very high energy and the other forces them into an undulating motion. Under these conditions, electrons emit X-radiation that is both highly energetic (‚hard‘) and highly intense, and is therefore ideal for probing the microscopic structure of matter. Now, physicists based at the Laboratory for Attosecond Physics (LAP) at LMU Munich and the Max Planck Institute of Quantum Optics (MPQ) have developed such a laserdriven X-ray source for the first time. With the aid of two laser pulses, the researchers have generated ultrashort bursts of X-rays with defined wavelengths tailored for different applications. The new source can image structures of varying composition with a resolution of less than 10 micrometers. This breakthrough opens up a range of promising perspectives in materials science, biology and – in particular – medicine.

research — In 1961, only shortly after the invention of the first laser, scientists exposed silicon dioxide crystals (also known as quartz) to an intense ruby laser to double its frequency, i.e., to change its colour from the visible to the ultraviolet, marking the advent of nonlinear optics and photonics. Now, researchers around Dr. Eleftherios Goulielmakis of the Attoelectronics Research Group at the Max Planck Institute of Quantum Optics in Garching, flashed an intense ultrashort laser pulse on thin films of the same material as in the mentioned pioneering experiment, and succeeded to convert laser light into radiation having a frequency more than 20 times higher than that of the laser, i.e., into the extreme ultraviolet range of the spectrum. The laser pulses used comprised merely of a single oscillation of their wave cycle and allowed the scientists to drive the motion of electrons inside the crystal lattice extremely fast. As the electrons of the material bounced on the lattice potential formed by the atoms in the crystal, they radiate and thus convert the energy taken up by the laser light into extreme ultraviolet radiation. The experiments pave the way towards new solid-based photonic devices. Because the motion of the electrons driven by the laser pulse probes the properties of the solid, measurements of the emitted radiation lead to a deeper understanding of the structure and the inner workings of solids.

research — With the aid of extremely short and highly intense pulses of laser light, scientists have made great strides in their efforts to observe and control particle motions outside the confines of atomic nuclei. Indeed, the future of electronics lies in optical control of electron flows. That would enable data processing operations to be performed at frequencies equivalent to the rate of oscillation of visible light – some 100,000 times faster than is feasible with current techniques. To reach this goal, advances in laser technology are essential. Physicists at the Laboratory for Attosecond Physics (LAP), which is run jointly by LMU Munich and the Max Planck Institute of Quantum Optics (MPQ), has developed a novel light source that brings the age of optoelectronics closer. The team describes the new instrument in the journal “Nature Communications”.

research — Es ist eine kühne Zukunftsvision, die Ferenc Krausz umreisst, nicht weniger als eine Revolution der Krebstherapie: Vor den Toren Münchens, sagt der Forscher, könnte einmal ein medizinisches Zentrum entstehen, dessen Kernstück ein mächtiges Laserlabor sei. Darum gruppieren sich Untersuchungs- und Betreuungsräume für Patienten, die mit hochenergetischer Laserstrahlung von Kopf bis Fuss auf Tumore untersucht werden. Ionenstrahlen, die ebenfalls von Lasern angetrieben werden, würden unmittelbar danach die entdeckten Wucherungen vernichten. Der Patient könnte kuriert die Heimreise antreten.

research — How fast do electrons whiz through the atomic layers of a crystal lattice? An international team of scientists led by researchers from the Technische Universität München (TUM) joined by colleagues from the Max Planck Institute of Quantum Optics (MPQ) in Garching, the Ludwig-Maximilians-Universität Munich and the Technical University of Vienna has now performed an experiment for investigating this fundamental question. The researchers measured the time needed for electrons to travel through a film consisting of a few layers a of magnesium atoms.

research — Ultra-short and extremely strong X-ray flashes, as produced by free-electron lasers, are opening the door to a hitherto unknown world. Scientists are using these flashes to take »snapshots« of the geometry of the tiniest structures, for example, the arrangement of atoms in molecules. To improve not only spatial but also temporal resolution requires further knowledge about the precise duration and intensity of such X-ray flashes. An international team of scientists has recently tackled this challenge.

research — Next-generation approaches to the production of ultrashort flashes of laser light – the so-called third generation of femtosecond laser pulses – are stimulating further advances in the investigation of ultrafast processes in the realm of the microcosmos. In the foreseeable future, the new techniques will permit the motions of subatomic particles to be observed in far greater detail than has been possible hitherto. In the new journal Optica, published under the auspices of the Optical Society of America, researchers led by Prof. Ferenc Krausz of the Laboratory for Attosecond Physics (LAP) at the Max Planck Institute for Quantum Optics (MPQ), together with a team based at Ludwig-Maximilians Universität (LMU), in Munich describe the underlying technology and the prospects that it will open up.

research — Chemical bonds between carbon and hydrogen atoms are amongst the strongest in nature and their selective breaking, in particular in symmetric molecules, is of interest to chemical synthesis and the development of new biologically active molecules. An international team of scientists has now demonstrated that ultrashort light pulses with perfectly controlled waveforms can selectively break C-H bonds in acetylene ions. The researchers demonstrated that a suitable choice of the laser-pulse waveform leads to breaking of the C-H bond on the left (or right) side of the symmetric H-C≡C-H molecule. The scientists propose that their results can be understood by a new quantum control mechanism based on light induced vibration (Nature Communications, DOI:10.1038/ncomms4800, 8 May 2014 ).

research — Light waves have the potential to boost the efficiency of conventional electronics by a factor of 100,000. In a review article that appears in “Nature Photonics” on March 14^th, Prof. Ferenc Krausz of the Laboratory for Attosecond Physics (LAP) at the Max-Planck-Institut für Quantenoptik and the Ludwig-Maximilians-Universität München and his co-author Prof. Mark Stockman of Georgia State University (GSU) in Atlanta describe how this vision may one day come true. In their scenario, one would exploit the electric field of laser light to control the flow of electrons in dielectric materials, which, in turn, may modulate transmitted light and switch current in electronic circuits at light frequencies. Visible light oscillates at frequencies of about 10¹⁵ cycles per second, opening the possibility of switching light or electric current at rates in this range. And since both signals can also carry information, innovative optoelectronic technologies would enable a corresponding increase in the speed of data processing, opening a new era in information technology. The authors review the novel tools and techniques of attosecond technology, which may play a crucial role in making the above advances actually happen.

research — A team in the Laboratory for Attosecond Physics (LAP) at the Max Planck Institute for Quantum Optics has taken another step toward the achievement of complete control over the waveform of pulsed laser light. Together with colleagues based at LMU and the Technical University of Munich (TUM), they have constructed a detector which provides a detailed picture of the waveforms of laser pulses that last for a few femtoseconds (1 fs = 10^-15 seconds). Unlike conventional gas-phase detectors, this one is made of glass, and measures the flow of electric current between two electrodes that is generated when the electromagnetic field associated with the laser pulse impinges on the glass. the researchers can then deduce the precise waveform of the pulse from the properties of the induced current. Knowledge of the exact waveform of the femtosecond pulse in turn makes it possible to reproducibly generate light flashes that are a thousand times shorter – lasting only for attoseconds (1 as = 10^-18 sec) – and can be used to study ultrafast processes at the molecular and atomic levels (Nature Photonics, 12. January 2014)

research — A stopwatch made of light can determine the duration of extremely brief electron flashes. Teams based in the Laboratory for Attosecond Physics (LAP) at LMU and at the Max Planck Institute of Quantum Optics have, for the first time, succeeded in measuring the lengths of ultrashort bursts of highly energetic electrons using the electric fields of laser light. Such electron pulses, which behave like ultrashort matter waves, provide time-resolved recordings of processes taking place in molecules and atoms, enabling elementary particles to be "filmed" in four dimensions. The new stopwatch for electrons now permits even more precise investigations of the motions of electrons and atoms on nature’s smallest scales.

research — In many ways, traditional chemical synthesis is similar to cooking. To alter the final product, you can change the ingredients or their ratio, change the method of mixing ingredients, or change the temperature or pressure of the environment of the ingredients. Like an accomplished chef, chemists have become very skilled at the manipulation of these parameters to produce many of the products that make our lives better.

research — Electrons are no slouches. In fact, they move so fast that they are hard to pin down. Nowadays these elementary particles can indeed be imaged, but what one gets are single, isolated snapshots. So the dispersion of free electrons over time has so far been impossible to observe directly. But now research groups based at LMU’s Laboratory for Attosecond Physics (LAP) and the Max Planck Institute for Quantum Optics (MPQ) in Garching, in collaboration with colleagues at Friedrich Schiller University in Jena have come up with a laser configuration that will make it possible to follow the dynamics of electrons essentially by filming them. The team has used a high-power laser to produce trains of attosecond pulses at a rate of 78 million per second, with each train containing around 20 individual flashes, each lasting less than a femtosecond. With this high repetition rate, it should be possible to characterize the behavior of electrons, whose quantum states fluctuate extremely rapidly, with greater efficiency than ever before. The breakthrough thus heralds a new era in the observation of this type of elementary particle. (Nature Photonics, July 7, 2013)

research — Electrons with a velocity close to the speed of light are hard to control. Using them as a tool for applications at the frontier of ultrafast physics requires them to be packed into extremely short pulses with tunable energy. A team around Laboratory for Attosecond Physics (LAP) group leaders Dr. Laszlo Veisz and Prof. Stefan Karsch, both based at Max-Planck-Institute for Quantum Optics (MPQ) has now achieved that feat by using a laser-driven accelerator. They created electron pulses with few-femtosecond duration, whose many individual particles all have nearly the same, but widely tunable energy. These monochromatic electron pulses can be used to create ultrashort flashes of light in the extreme ultra-violet or even X-ray range, who in turn are a versatile tool for probing fast processes in the microcosm. (Physical Review Letters, May 02, 2013).