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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 âˆ¼30-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.