The domain wall regions in periodically poled MgO-doped LiNbO3 （PPMgLN） crystal are examined by using second harmonic generation （SHG）. The results show that the average domain walls that separate the individual domains have a width in the order of about 1 μm, and the walls are neither completely smooth nor uniform along the walls from the imaging of the SHG. It is proposed that the origin of the second harmonic signal in the regions around domain wall is attributed to the non-180° domain walls in the ferroelectric domains.
A hexagonal array grating based on selective etching of a 2D ferroelectric domain inversion in a periodically poled Mg O-doped Li Nb O3 crystal is fabricated. The effects to the diffractive self-imaging as a function of diffraction distance for a fixed phase difference and array duty cycle of the grating is theoretically analyzed.The Talbot diffractive self-imaging properties after selective etching of a 2D ferroelectric domain inversion grating under a fixed phase difference are experimentally demonstrated. A good agreement between theoretical and experimental results is observed.
