Influence of annealing temperature on domain shape of periodically poled LiNbO3 for Ti:LN waveguides

Periodically poled LiNbO3 (PPLN) has been fabricated with a 16.6 μm domain-inverted period, a 3.0 μm thick photoresist grating, and a 3.3 μm pattern open width through the electric field poling process using the liquid electrode technique. The average duty cycle for the fabricated PPLN was measured to be 49.9 ± 3.3%. The effect of annealing temperatures on the domain shape of PPLN was investigated in the range of 300 to 800 °C. At 300 °C, residual stress was not relieved completely. As the annealing temperature increases above 800 °C, the domain shape changes. However, no domain damage was observed for annealing temperatures from 400 to 700 °C. The best annealing temperature for the suppression of domain damage and the improvement in the crystalline quality was found to be 400 °C.