Ultra-intense & Ultra-fast

laser-matter interaction

Plasma_mirror.html

Robin Marjoribanks Group

Department of Physicshttp://www.physics.utoronto.ca
University of Torontohttp://www.utoronto.ca

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...’

Isaac Asimov

 
Extreme Interaction Physics

Virtually since the invention of the laser, physicists have anticipated producing light with such high intensities that normal radiative perturbation theory no longer makes sense. In the last decade of new high-power lasers, experimental physics has leaped past this boundary. New fields of basic atomic, molecular, optical, and plasma physics are springing up, characterized by relativistic-intensity optical fields and high-energy-density environments. Light intensities now available in the laboratory are reaching about 21 orders of magnitude (1,000,000,000,000,000,000,000 times) the brightest sunlight shining on the earth.

The effect of matter-interaction on the ultra-intense laser pulses is extremely nonlinear -- the relativistic oscillation of electrons at the surface of a plasma can make hundreds of harmonics of the laser pulse, reaching well into the XUV and soft x-ray spectrum. This huge bandwidth supports extremely brief pulses, in the attosecond range. The optical physics of these pulses is interesting on its own, but attosecond pulses are enormously important as probes for atoms, molecules and biology.

The effect of interaction on a solid is also extreme: the strong electric fields ionize any matter in femtoseconds, freeing and then driving electrons, and the relativistically moving electrons ‘sandblast’ the matter -- producing more ionization through collisions.  The matter will heat from room temperature (~300K) to about 10 million Kelvin in just a few tens of femtoseconds: a change of about 1019 Kelvin per second!  Measurement of high-temperature, high-density laser-produced plasmas generally depends on line and continuum spectroscopy of their x-ray emission. The historical basis of such spectroscopy is the study of stars and novae; laboratory plasmas are now reaching toward temperatures and densities comparable to stellar interiors, for which the formation of spectral lines is not well understood. With time-integrated and time-resolved x-ray spectroscopy, we are studying ionization, and the formation of spectral lines in non-equilibrium laser-produced plasmas.

Our current high-intensity collaborations include projects with the University of Oxford (UK), the Laboratoire d’Optique Appliquée (ENSTA, France), and others.  In 2016 we have experiments planned on the ELFIE laser at Ecole Polytechnique (France) and on LCLS, the x-ray free-electron laser system at SLAC (Stanford University, CA), as well as tentative plans on ORION (UK) and the Jupiter laser facililty at LLNL (USA).

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