B-Integral Measurement on High-Power Laser Facility based on Off-Axis Aberration

We propose a spatially resolved B-integral measurement method for high-power laser drivers, based on coma aberration off-axis aberration characterization. Theoretical analysis confirms the feasibility and high precision of this approach, where intensity modulation in a coma-shaped form is intentionally introduced into the laser system, imprinting the nonlinear phase modulation with a corresponding aberration profile. The B-integral is then extracted by measuring the coma component of the output beam via a Shack-Hartmann (SH) sensor. Experimental results demonstrate a 5.8% deviation between the measured and simulated B-integral values for coma aberration, significantly outperforming the 67.4% error observed with defocus-based measurements. This method requires no modifications to the laser setup, offers single-shot measurement capability, and achieves high accuracy and excellent repeatability. By directly quantifying wavefront phase distortions, it provides a practical solution for nonlinear phase modulation diagnostics in high-power laser systems.