Robust poling and frequency conversion on thin-film periodically poled lithium tantalate

We explore a robust poling method for periodically poled thin-film lithium tantalate (PP-TFLT) by systematically varying poling parameters and confirming the quality of inverted domains with second-harmonic microscopy. We find a periodic poling process that is insensitive to acoustic-grade or optical-grade thin film, electrode material, and the presence of an oxide interlayer. By using a single high-voltage electrical pulse with a peak voltage time of 100 ms or less and a ramp-down time of 90 s, rectangular poling domains are established and stabilized in the PP-TFLT. We employ our robust periodic poling process in a pole-after-etch approach to produce PP-TFLT ridge waveguides with normalized second-harmonic generation (SHG) conversion efficiencies of 208% W⁻¹ cm⁻² from 1550 to 775 nm, which is in line with the theoretical value of 244% W⁻¹ cm⁻². This work establishes a reliable poling process and demonstrates SHG from the telecommunications band to the near-visible band using thin-film lithium tantalate, expanding the capabilities of the platform for frequency mixing applications in quantum photonics, sensing, and spectroscopy.