Micro-domain initialization in photorefractive ferroelectrics

The possibility of micro-domains origin in photoreffactive ferroelectric crystals near charged mesoscale defects inside the crystal has been studied. For simplicity this defect is simulated by electrically charged sphere, but the micro-domain is considered as a cylinder with infinitely thin domain walls. It has been shown that the charge of defect must exceed the threshold value for micro-domain appearance. Depending on electrical and geometrical parameters of charged defect the needle-like or lens-like micro-domains can be generated.