Quasi-phase matching lithium niobate, periodically poled via liquid electrodes

We have achieved reliable periodic poling of z-cut lithium niobate in 0.2 mm thick samples, patterned with photoresist on one face and subjected to pulsed electric fields via liquid electrodes. Our set-up was a further development of the one used by Camlibel. Filter paper was soaked in a solution of LiCl in water and placed on both sides of a sample with a photoresist pattern on one side (1 micrometre of standard photoresist acts as an effective barrier to domain inversion). This sandwich was then clamped between electrodes connected to ground and a high-voltage pulse generator. The pulse amplitude was 4.5 kV. We found that the single most important feature during inversion is that the transferred charge should be twice the spontaneous polarization times the desired area of inversion. The domains went all the way through the substrate, with a slight random variation in the position of the domain walls on the planar electrode side