Systematic Analysis of Ferroelectric Domain Dynamics in Periodically Poled Lithium Niobate Waveguides Using Two-Photon Microscopy and Digital Imaging Processing

We present a characterization and analysis methodology suitable for volume production for characterizing and optimizing x-cut thin-film periodically poled lithium niobate (PPLN) devices using two-photon (2P) microscopy with quantitative image processing. This method enables direct extraction of key structural parameters, such as duty cycle, phase-matching behavior, and domain uniformity, across large device sets in a non-destructive manner. By correlating 2P microscopy-derived structural metrics with systematic variations in poling conditions, we establish a scalable, image-driven approach for evaluating and improving PPLN fabrication. The resulting workflow supports wafer-level process development and accelerates the manufacturing and packaging of lithium niobate photonic integrated circuits (PICs).