Patent ID: 7668410

Claim:
A method of producing a polarization inversion part by electric field polling process using a comb electrode having a plurality of electrode portions, a feeding portion provided on one surface of a substrate of a ferroelectric single crystal and of single domain, an opposing electrode, and a power source directly connected only to said base portion and said opposing electrode; wherein said polarization part is produced by an electric field formed from each of said plurality of conductive portions toward said opposing electrode in a “B” direction opposite a polarization axis of said substrate of said ferroelectric single crystal when a voltage is applied between said base portion and said opposing electrode, wherein an optical waveguide is not present in said substrate of said ferroelectric single crystal, wherein said electrode portion comprises a base portion extending from said feeding portion and a plurality of conductive portions separated from said base portion and arranged in series between said base portion and said opposing electrode, and wherein said conductive portion at the tip end of said electrode portion is provided between other conductive portions of said plurality of conductive portions and said opposing electrode, said conductive portion at the tip of said electrode directly opposes said opposing electrode and has a length smaller than the length of the conductive portion nearest to said base portion.