SHG interference microscope as a tool of nondestructive observation of ferroelectric 180° domain structures

Using the interference SHG microscope, ferroelectric 180° domain structure can be nondestructively observed. The principle of the microscope is to use the fact that up and down domains produce optical second harmonic waves with same amplitude but opposite phase. Then they are superposed with homogeneous SH wave from a standard SHG plate. The phase is controlled by a glass plate to get maximum contrast. This microscope was successfully applied to domain structure observations in BaTiO3 and domain reversal process in MgO:LiNbO3 under the pulsed-electric field. The possibility of the domain structure observation along the axial direction is also discussed.