Beecroft Building, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Professor Alexander Thomas, Center for Ultrafast Optical Science, University of Michigan
Abstract
Extreme ultraviolet (XUV) light sources allow for the probing of bound electron dynamics on attosecond scales, interrogation of high-energy-density and warm dense matter, photolithography of nanometer-scale features, and access to novel regimes of strong-field quantum electrodynamics. Despite the importance of these applications, coherent XUV light sources remain relatively rare, and those that do exist are limited in their peak intensity and spatio-polarization structure. Frequency upshifting of an optical laser pulse in the co-moving refractive index gradient of relativistic phase-velocity plasma wave is one method for producing short wavelengths at high intensity.
In this seminar, I will present recent theoretical results showing that plasma waves can produce arbitrarily high-frequency upshifts of `relativistically intense' light pulses and preserve the spatio-polarization structure of the original pulse. Ab-initio quasi-3D, boosted-frame electromagnetic particle-in-cell simulations show the formation of attosecond duration XUV vector vortex pulses with ∼30-nm wavelengths, nearly flat phase fronts, and intensities exceeding $10^{20}$ W/cm$^{2}$. By focusing with a plasma lens, it may be possible to achieve even higher intensities for which the use of XUV laser light in laser-beam collisions enables studies of the most extreme regimes of QED. I will review previous experimental results and discuss the outlook for the experiments required to validate these new findings.