High-quality periodic poling and efficient domain characterization of x-cut lithium niobate on insulator

Lithium niobate on insulator (LNOI) serves as a promising platform for the advancement of nonlinear integrated photonics. There is a high demand for high-quality periodic poling and an efficient characterization method compatible with wafer-scale LNOI to achieve frequency conversion utilizing the quasi-phase matching technique. In this study, we conduct a systematic investigation into the periodic poling of 600-nm-thick x-cut congruent LNOI. We introduce spike pre-pulses to enhance poling fidelity and uniformity while optimizing key poling waveform parameters, including peak voltage, pre-pulse number, and peak duration. A rapid and cost-effective polarization-contrast microscopy in the reflection mode is employed for domain characterization, and its reliability is validated through comparison with piezoresponse force microscopy. Our results demonstrate periodic poling with high fidelity, excellent uniformity, and a duty cycle close to 50% for a poling period of 5 μm. The proposed poling methodology and characterization approach offer a scalable solution for periodic poling of wafer-scale LNOI nonlinear integrated photonic devices.