Optimization of ultraintense laser focal spots and suppression of wavefront aberrations are critical for enhancing peak intensity and improving laser-driven ion acceleration performance. However, real-time optimization feedback from in-situ, on-target focal diagnosis remains a long-standing challenge in high-intensity laser experiments. This report presents a focus optimization method based on second-harmonic far-field patterns generated from laser-thin foil interactions. The harmonic far-field naturally encodes the astigmatism features of the incident laser, enabling real-time feedback to guide off-axis parabolic mirror adjustment for aberration compensation. Experimental verification demonstrates improvements in the cutoff energy, particle yield, and spatial symmetry of accelerated proton beams.

high-intensity laser-plasma interaction,laser-driven ion acceleration