Promoting Periodical Poling in Lithium Niobate Crystal Through Surface Acoustic Wave‐Induced Local Lattice Activation

Abstract Achieving precise construction of ferroelectric domain structure in lithium niobate (LN) crystals holds significance for expanding the applications of periodically poled lithium niobate (PPLN), especially in nonlinear frequency conversion. However, challenges exist during the application of electric field for poling, especially for small‐period PPLN crystals, where ferroelectric domains in LN crystals tend to unevenly expand laterally, making it hard to precisely control the domain structures. LN, as a piezoelectric crystal, has the capability to generate energy‐carrying surface acoustic waves (SAW). Herein, an method is presented to optimize the periodic poling process by integrating SAW and poling on a LN chip, which remarkably reduces the poling electric field by 10%, attributed to the enhanced local lattice vibrations during SAW propagation. The integrated SAW and poling chip achieves a 9 µm‐period PPLN crystal. Through second harmonic generation, a nonlinear light conversion from 1158 to 579 nm is realized, exhibiting a nonlinear optical efficiency up to 17.4%. This efficiency aligns with the theoretical prediction, validating the high‐quality domain structure. This integrated chip provides a unique opportunity for manipulating ferroelectric domain with high‐precision, benefiting a wide range of applications in nonlinear‐optics, ferroelectrics, and integrated optics.