The improvement of laser intensity from ~10²³ W/cm² to >10²⁴ W/cm² remains a challenging endeavor because it is extremely difficult to fabricate large-aperture pulse compression gratings with existing manufacturing technologies. In this report, we propoase a method for manipulating the energy mergence between two in-phase seed lasers by two obliquely incident guiding lasers whose initial phase is π and π/2 ahead of the seed laser. It is found that due to the repulsion and energy transfer of the guiding laser, the peak intensity of the merged light is amplified by more than five times compared to the seed laser. For an inhomogeneous plasma with an exponential increase in density, almost an order of magnitude enhancement of laser intensity is even possible owing to the compression and focusing effects.  In particular, with a seed laser intensity of 3 × 10²³ W/cm² and power of ~38 PW, one can obtain 3 × 10²⁴ W/cm² intensity and up to ~50% energy conversion efficiency from the initial seed laser to the focused laser. This may pave the way to the new research field of plasmas-based nuclear physics in the upcoming laser facilities. 

Field amplification, energy mergence, multiple relativistic femtosecond laser pulses, plasma