Towards Megajoule X-ray Lasers via Relativistic 4-Photon Cascade in Plasma

An extraordinarily efficient mechanism, operating at high laser intensities and powers, is identified for spectral transferring huge laser energies to shorter ultraviolet and x-ray wavelengths. With megajoule laser energies currently available at near-optical wavelengths, this transfer would enable megajoule x-ray lasers, a huge advance over the millijoules x-ray pulses produced now.