Full-field stress measurement based on polarization ptychography.

In a high power laser system, the stress in large-aperture optical component could affect the system beam quality and safe operation. But studies on stress distribution and influence mainly focus on the finite element analysis. A new stress measurement method for large-aperture sample, which combines the ptychography with the polarization measurement technique, is presented. The birefringent sample is placed in the parallel probe-forming path. By the complex amplitude reconstructions of probes carrying stress information under different polarization states, the separation of two principal stress components is realized and quantitative full-field stress information is provided. The theoretical derivation and experimental implementation about how to extract strong stress information from phase are illustrated. The feasibility of this method is verified through a classic diametrically compressed disc, and the result for each stress component agrees well with the theoretical model. The proposed method avoids the scanning movement of sample and has a simple structure and strong anti-interference ability. It can be further combined with single-shot PIE techniques for rapid and online measurement, which provides a practical measurement means for the study of stress in large-aperture optics. [ABSTRACT FROM AUTHOR]