Polarization inversion method for ferroelectric substances

A polarization inversion method for a ferroelectric substance, comprising the steps of:

• i) forming a pattern electrode, which has a predetermined pattern, and a connecting electrode, which is electrically connected to the pattern electrode, on one surface of a single-polarized ferroelectric substance crystal,
• ii) locating a corona wire at a position which stands facing the other surface of the ferroelectric substance crystal, and
• iii) applying an electric field across the ferroelectric substance crystal with a corona charging technique by use of the corona wire and the pattern electrode, whereby a polarization inversion region having a shape corresponding to the predetermined pattern of the pattern electrode is formed in the ferroelectric substance crystal,
• wherein the application of the electric field is performed in a state, in which an electrical insulating material is located on the other surface of the ferroelectric substance crystal and at a position that corresponds to at least a position of a certain area of the connecting electrode.