Domain dynamics in coercive-field engineered sub-µm periodically poled Rb-doped KTiOPO4

Abstract

Nonlinear optical interactions involving counter-propagating photons are of great interest for both classical and quantum optical applications. However, their use is sparsely spread due to the fact that they require quasi-phase-matched devices with sub-µm periods. A recent breakthrough has been the fabrication of bulk sub-µm domain gratings in Rb-doped KTiOPO4 by creating a grating of low- and high- coercive field regions in the crystal via periodic ion exchange, so-called coercive-field engineering. Here, we investigate the physical mechanisms behind this method and study the interplay between the ion-exchanged grating properties and the ferroelectric domain dynamics. Furthermore, we investigate the scalability of the method by studying the domain morphology of sub-µm periodically poled crystals with periods ranging from 755 to 433 nm and correlating it to that of the ion-exchanged regions. We show that the formation of sub-µm domain gratings is governed by the depth, shape, and critical ion-concentration of the ion-exchanged volume and that it is independent of the poling period. These findings are crucial for further scaling the coercive field engineering technique to even shorter poling periods and larger aperture periodically poled crystals.