Ultrahigh intensity lasers have been developed for the exploration of strong field physics in a number of institutes around the world. At Center for Relativistic Laser Science of Institute for Basic Science two PW laser beamlines have been utilized for investigating relativistic laser- matter interactions, and one of them has been upgraded recently to a 20 fs, 4 PW laser . With the PW lasers we succeeded in generating multi-GeV electron beams and collisionless electrostatic shock. We plan to carry out the Compton backscattering to generate MeV gamma- rays from the interaction of a GeV electron beam and another laser beam, offering an opportunity to measure strong field QED effects. In addition, we plan to carry out the investigation of laboratory astrophysics, such as plasma instabilities, shock acceleration, and magnetic reconnection.
 J. H. Sung et al., “4.2 PW, 20 fs Ti:Sapphire Laser at 0.1 Hz,” Opt. Lett. 42, 2058 (2017).