Extremely high power lasers at the 10 petawatts class have become available recently and some 100 petawatts class lasers are already under construction, e.g., at the SEL facility in Shanghai. Theoretically, 10–100 petawatts facilities can deliver laser pulses with unprecedented intensities of \(10^{23}~{\mathrm{W\,cm}}^{-2}\) – \(10^{24}~{\mathrm{W\,cm}}^{-2}\) . Under such conditions, laser–plasma interactions will enter a regime dominated by strong-field quantum electrodynamics (QED) effects, where generation of abundant high-energy photons and electron–positron pairs is expected via the nonlinear Compton scattering and nonlinear Breit–Wheeler processes. In this paper, we present a review on our recent related studies on this topic, which include the QED particle-in-cell (PIC) code development and new physics of laser–plasma interactions found in this regime. To study the QED-dominant laser–plasma physics, firstly we have developed QED-PIC codes, which include the radiation damping, nonlinear Compton scattering, nonlinear Breit–Wheeler processes, as well as spin polarization for photons, electrons, and positrons. With the help of QED-PIC simulations, a few unique features of laser–plasma interactions associated with the QED effects are found. For example, it is found that an ultrarelativistic laser can become opaque when it propagates in underdense plasma due to the triggering of different QED processes. Collimated ultrabright gamma rays can be produced from a solid wire by tightly focusing a petawatt class laser along the wire. Generation of dense polarized positrons is found from a solid target irradiated by intense laser pulses in the QED regime. Moreover, polarized gamma rays can be produced by collision of two ultrarelativistic electron beams without using lasers.
