Optical waveguide substrate manufacturing method

A method of producing an optical waveguide substrate comprising a channel optical waveguide with a periodic domain inversion structure formed therein, the method comprising the steps of:

• applying a voltage on an interdigitated electrode provided on one main face of a single-domain ferroelectric single crystal substrate to form a periodic domain inversion structure;
• removing the interdigitated electrode;
• and
• forming the optical waveguide in the ferroelectric single crystal substrate,
• wherein a projected location P2 of an optical intensity center P1 of the optical waveguide on the one main face is kept away from a projected location P0 of the end of the interdigitated electrode on the one main face.