Ptychographic Mueller matrix imaging: in-situ system calibration and evaluation

Calibration is crucial for accurate polarimetric systems. In this Letter, we propose a hybrid strategy to in-situ calibrate the ptychographic Mueller matrix imaging (PMMI) system [Opt. Lett.49, 6409 (2024)10.1364/OL.539100], extending our previous work. The proposed approach combines the eigenvalue calibration method to determine the polarimetric matrix of the polarization state generator, followed by a model-based calibration procedure to determine the polarimetric properties of the polarization state analyzer. With this strategy, the PMMI system can be in-situ calibrated within the actual operational configuration, which can effectively compensate the imperfections in polarization components and mounting errors. Experiments were conducted on a home-built PMMI prototype, and an isotropic USAF-1951 resolution target with theoretical identity Mueller matrix is tested to quantitatively evaluate the system performances. Experimental results indicate that after calibration, the measurement accuracy and precision of the imaging Mueller matrix are 0.01 and 0.005, respectively, and the measurement repeatability is 0.005. The proposed in-situ calibration technique and comprehensive system evaluation render the PMMI a powerful and quantitative tool for the characterization of nanomaterials and nanostructures.