Real-time determination of beam propagation factor by Mach–Zehnder point diffraction interferometer

Based on a novel Mach–Zehnder point diffraction interferometer, a real-time method to determinate beam propagation factor M 2 of laser beams is presented. By using the proposed point diffraction interferometer, the intensity profile and wavefront of laser beam are completely extracted from a single interferogram in one-shot measurement. Knowing the complex field of laser beam yields the beam's propagation parameters such as beam propagation factor M 2 conform to the ISO standard method. The experimental method is simple, fast and operates without movable parts, which is allowed to investigate laser beams in conditions inaccessible using the existing method.