Influences of focusing conditions on optical poling in lithium niobate using a 1035 nm femtosecond fiber laser

In this study, we demonstrate the optical induction of ferroelectric domain inversion on the -z surface of lithium niobate crystals using a 1035 nm femtosecond fiber laser. We investigate the effects of laser power and focusing parameters on domain morphology. The results revealed that domains exhibit an irregular random distribution at low power, whereas regularly arranged domains were formed near the crystal damage threshold. Furthermore, with sufficiently high power, lens focusing enables the fabrication of uniformly sized domains exceeding 100 µm. The results suggest potential applications for controlling domain morphology and the duty cycle, and fabricating ferroelectric functional devices.