Method of producing domain inversion parts and optical devices

A method of producing domain inversion part in a substrate of a ferroelectric single crystal by providing a comb electrode on a first main face of said substrate of said ferroelectric single crystal of a single domain and a uniform electrode on a second main face of said substrate and by applying a voltage on said comb electrode and said uniform electrode, said method comprising the steps of:

• laminating an underlying substrate on said substrate of said ferroelectric single crystal, said underlying substrate comprising a main body, a first conductive film provided on a first main face of said main body and a second conductive film provided on a second main face of said main body so that said uniform electrode is electrically conducted with said first conductive film;
• and
• applying a voltage on said comb electrode and said second conductive film to form a domain inversion part in said substrate of said ferroelectric single crystal.