Optical modulator

An optical modulator, comprising:

• a base part which is a plate-like member formed of a material of which the refractive index is changed by an electric field, having a periodically-poled structure in which a first polarization part and a second polarization part which are opposite in the direction of polarization produced when said electric field is applied are alternately arranged in a polarization-part array direction;
• and
• a modulation part having a first electrode portion provided on one main surface of said base part and a second electrode portion provided on the other main surface of said base part, which applies voltage between said first electrode portion and said second electrode portion to thereby cause a periodic change of said refractive index in said polarization-part array direction in said periodically-poled structure,
• wherein a linear light beam spreading out in said polarization-part array direction enters said base part from one end surface thereof, being guided inside said base part in a traveling direction in which said light beam is diffracted by said periodic change of said refractive index, and exits from the other end surface,
• said first electrode portion comprises a plurality of first electrodes arranged in an electrode array direction parallel to said polarization-part array direction or perpendicular to said traveling direction,
• each of said plurality of first electrodes is disposed on a polarization part group including a predetermined number of first polarization parts and/or second polarization parts which are arranged successively in said polarization-part array direction, and
• voltages applied between said plurality of first electrodes and said second electrode portion are equal and individually controlled.