Professor Simon Hooker

I study the interaction of very high intensity laser pulses with plasma and applications which arise from these, such as the generation of very short X-ray pulses and a new type of particle accelerator.

In high-harmonic generation (HHG) the highly nonlinear interaction between high-intensity laser pulses and atoms generates odd harmonics of the frequency of the driving laser. The harmonic order can reach several hundred, allowing the generation of coherent beams with nanometre wavelengths by visible driving lasers. My research group studies methods for increasing the efficiency of these sources and the application of HHG beams to imaging objects without the aid of conventional lenses (which are not readily available for X-ray wavelengths). In 'lensless imaging' one instead records the diffraction pattern produced by the object and deduces the spatial distribution of the object by employing numerical algorithms; it turns out that this can be done rather efficiently even though the important phase information is lost when the detector records the intensity (rather than amplitude) of the diffraction pattern.

At intensities of around 10²² W m^-2, laser pulses propagating through a plasma drive a longitudinal plasma wave which trails the laser pulse in much the same way a wake follows a boat travelling across water. The electric fields in the plasma wave can reach 100 kilovolts per micron, at least a thousand times bigger than the accelerating fields used in the LHC at CERN. Experiments performed by my group and a team at Lawrence Berkeley National Laboratory were the first to demonstrate laser-driven acceleration of electrons to an energy of 1 GeV. This beam energy is typical of that used in `stadium-scale' synchrotrons and free-electron lasers, but our plasma acceleration stage was only 30mm long! My research group and I are presently working on novel ways of driving the plasma wave, new kinds of waveguide capable of channelling very intense laser pulses over long distances, techniques to control the injection of particles into the plasma wave, and the application of laser-accelerated electron beams to generate ultrafast X-ray pulses.

In 2010 I was a co-recipient of the American Physical Society’s John Dawson Award for Excellence in Plasma Physics Research. Further information on my research group can be found at https://lpax.web.ox.ac.uk
 

At Merton I typically give undergraduate tutorials on: Mechanics and Special Relativity; and Atomic, Molecular, and Laser Physics. In previous years I have taught Optics and Electromagnetism. Within the Department I currently give lectures on Laser Physics and Optics.