All-optical nonlinear Compton scattering performed with a multi-petawatt laser

Light–matter interactions driven by ultrahigh-intensity lasers have great potential to uncover the physics associated with quantum electrodynamics (QED) processes occurring in neutron stars and black holes. The Compton scattering between an ultra-relativistic electron beam and an intense laser can reveal a new interaction regime, known as strong-field QED. Here we present an experimental demonstration of nonlinear Compton scattering in a strong laser field, in which a laser-accelerated multi-gigaelectronvolt electron scatters off hundreds of laser photons and converts them into a single gamma-ray photon with several-hundred-megaelectronvolt energy. Along with particle-in-cell (PIC)-QED simulations and analytical calculations, our experimental measurement of gamma-ray spectra verifies the occurrence of Compton scattering in the strongly nonlinear regime, paving the road to examine nonlinear Breit–Wheeler pair production and QED cascades. Researchers demonstrate nonlinear Compton scattering in a strong laser field, in which a laser-accelerated multi-GeV electron scatters off hundreds of laser photons and converts them into a single gamma-ray photon with several-hundred-MeV energy.