Off-axis aberration-based B-integral measurement method for a high-power laser facility

Abstract

We propose a spatially resolved B-integral measurement method for high-power laser drivers based on off-axis aberration characterization. Theoretical analysis confirms the feasibility and high precision of this approach, in which coma-shaped intensity modulation is intentionally introduced into the laser system, imprinting nonlinear phase modulation with a corresponding aberration profile. The B-integral is then extracted by measuring the coma component of the output beam using a Shack–Hartmann sensor. The experimental results demonstrate a 5.8% deviation between the measured and simulated B-integral values for coma aberration, showing that the proposed method significantly outperforms the defocus-based measurement method (67.4% error) in terms of error reduction. This method does not require modifications to the laser setup, offers a single-shot measurement capability and achieves high accuracy and excellent repeatability. The direct quantification of wavefront phase distortions provides a practical solution for nonlinear phase modulation diagnostics in high-power laser systems.