The effect of the ferroelectric domain walls in the scanning near field optical microscopy response of periodically poled ba2nanb5o15 and linbo3 crystals

A study of Ba2NaNb5O15 and LiNbO3 crystals with periodic ferroelectric domain structures using the scanning near field optical microscopy technique is reported. Optical contrast is observed in the regions of ferroelectric domain boundaries and it is analysed using beam propagation method modelling. This reveals that the optical contrast, a consequence of changes in the refractive index, is not due to variation of the waveguide-coupling efficiency, and supports the hypothesis that it is associated with the domain array, which is related to the size of the domain