Extreme optical field amplification via multiple ultraintense femtosecond lasers merging and focusing

Ultra-intense lasers play a crucial role in the investigation of strong-field quantum electrodynamics. In this work, we propose a method for generating laser pulses with an intensity exceeding 10²⁴ ~W/cm² by irradiating a two-stage plasma target with four ultra-intense femtosecond laser beams. Two-dimensional particle-in-cell simulations demonstrate that, during the first stage, the four seed beams emerge into a single beam, with its intensity nearly doubling as it propagates through a uniform-density plasma. In the subsequent stage, the merged beam is reflected and compressed by a gradually denser plasma, resulting in beam front steepening and focusing. Despite energy losses due to the generation of gamma photons, the output beam achieves an intensity enhancement of one order of magnitude, reaching up to 10²⁴ ~W/cm², with a combining efficiency of 33.7%. Our proposed scheme offers a promising approach for generating extreme light and is expected to advance studies on particle acceleration and radiation generation governed by quantum electrodynamics.