Single-exposure beam quality analysis via lens-free coherent amplitude modulation imaging

A single-exposure method for complex amplitude reconstruction in beam quality analysis is proposed, utilizing lens-free coherent amplitude modulation imaging (LF-CAMI). This approach leverages a partially saturated diffraction pattern to reconstruct the complex amplitude of a measured laser beam. The corresponding intensity images near the beam waist along the axial direction are determined directly via the Fresnel diffraction formula. Spatial beam parameters, including the beam quality factor M², are then calculated following the ISO 11146-1 standard. The feasibility of the proposed method is validated through theoretical analysis and experiments, targeting both static and dynamic laser beams. Experimental results demonstrate that this method yields results consistent with those obtained using commercial beam quality analysis instruments while reducing the total measurement time by approximately 80%. The proposed method is compact, cost-effective, and immune to aberrations and offers a fast and accurate measurement process, making it particularly suitable for beam quality analysis in various laser systems, especially pulsed laser systems.