Controlled intense laser fields, X-ray pulses, attosecond metrology and spectroscopy
Prof. F. Krausz, Experimental Physics, LMU + MPQ
Main research areas: Synthesis of high-intensity light waves; attosecond X-ray pulses and measuring technique; laser-driven particle accelerators and coherent X-ray sources
Present-day microscopes allow structural investigations in the atomic-resolution range (~1 angstrom =10-10 m). By means of ultra-short laser pulses one can trace the motion of atoms on this length scale. The shortest laser pulses perform very few field oscillations and last just a few femotoseconds (1 femtosecond being a millionth of a billionth of a second). The resulting short exposure time allows snapshots of moving atoms and observation in slow motion. This provides modern experimental physics with tools for studying structure and dynamics with atomic resolution in time and space. Insight into the inner life of atoms call, however, for a time resolution in the attosecond region (1 attosecond being a thousandth of a femtosecond).
The Laboratory of Attosecond and High-Field Physics (LAP) developing tools and methods with which the motion of microscopic particles inside and outside atoms can be traced and controlled on a time scale of attoseconds. Scientists from Max-Planck-Institute of Quantum Optics and the Technical University of Vienna achieved a decisive step in this direction in 2002. They were able to generate high-intensity light pulses in which not only the brightness but also the exact temporal variation of the electric (and magnetic) field could be controlled. The perfect control of light waves thus afforded makes it possible for the first time to subject microscopic particles of matter to significant controlled forces by means of electric charges (electrons, protons).The first spectacular achievement of such hyper-fast control was to produce single flashes of soft X-radiation lasting a few hundred attoseconds. The strong laser field first ejects electrons from atoms and then immediately hurls them back to the atomic nucleus with great energy. The electrons recaptured by the atoms emit their energy in phase as short-wave X-ray flashes. The fast oscillating, strong electric field of the laser pulse here serves not only for generating the X-ray flash but also for measuring its duration. The new attosecond measuring technique recently allowed observation of processes in the electron sheath of atoms and was ranked by „Science” magazine among the ten most important achievements of the year 2002. In the next few years scientists at LAP will be engaged in developing high-power laser systems that will be unique, so-called light wave synthesizers. These transmit ultra-intense light wave packs that perform very few oscillations and have an identical and controlled wave form. These perfectly controlled light waves allow for the first time control of processes deep inside the electron sheath (in the so-called inner shells) of atoms. The scientists at MPQ are confident that one day they will also succeed in using attosecond X-ray pulses to represent in slow motion electrons moving inside atoms.
Synthesized, ultra-intense light waves also open the door to controlled acceleration of charged particles (electrons, protons) with laser light. The research here is expected to provide new knowledge of the inner life of atoms and the motion of microscopic particles in light fifields. This will make it possible, for instance, to develop compact sources of high-energy particle pulses and also photon pulses with hitherto unknown properties.
Contribution to IMPRS curriculum:
Photonics I: theory of light and its advanced applications
Lecturer: Ferenc Krausz (3+1 hours/week)
Content:
The lecture course introduces the four models of light: i) ray optics, ii) wave optics, iii) electromagnetic optics and iv) quantum optics, postulates their laws and present their applications with particular emphasis on those requiring the introduction of these successively more advanced [i) --> iv)] models.
Photonics II: intense-laser-matter interactions for science, technology and medicine
Lecturer: Ferenc Krausz (3+1 hours/week)
Content:
Generation and measurement of intense, ultrashort laser pulses. Nonlinear light-matter interactions at high intensities: generation of coherent soft X-rays and attosecond X-ray pulses. High-speed "photography" in the microcosm: capturing the motion of electrons and atoms with femto- and attosecond pulses. Laser-induced breakdown in dielectrics: micro- and nanomachining with lasers, nanophotonics. Pushing the limits of electronics: the THz laser oscilloscope. Medical applications: laser neuro-, eye and dental surgery; optical coherence tomography.