Generation of atto-zeptosecond X-rays through cross-collision between relativistic electron and tightly focused intense laser pulse

The generation of ultrashort pulses is a hot topic in ultrafast physics. In the framework of classical electrodynamics, the process of nonlinear cross Thomson scattering which involves sideways radiation generation by a high-energy single electron cross-colliding with a tightly focused circularly polarized intense laser pulse is investigated through numerical simulation. For spatial limited tightly focused laser pulses, the laser delay time determines the position the electron interacts with, so precise control of the laser delay time to ensure the electron collides with the laser center is the key to obtaining high-power radiation. Through the research on the time evolution of electron radiation, it is found that the nonlinear cross Thomson scattering power is related to the coupling of electron velocity and its acceleration, where the increase of the electron velocity is critical to obtaining higher-power radiation. For off-axis electrons, the increase in deviation distance mainly leads to a decrease in radiation power, rather than pulse width and central photon energy. For low initial energy electrons, the asymmetry brought about by cross-collisions will improve the spatial collimation. For high-energy electrons, the asymmetry is weakened but the spatial collimation is enhanced. Using a single electron with an initial energy of 100 MeV and a laser pulse with an intensity of about , hard -rays can be generated. This study reveals part of the mechanism of nonlinear cross Thomson scattering and provides the theoretical basis and parameter suggestions for the design of the next generation ultrashort high-energy pulse generator.