Patent ID: 7433111

Claim:
An electro-optic modulation device that includes an electro-optic crystal having a birefringence index changed by a coupled electric field, and one pair of electrodes disposed so as to have the electro-optic crystal interposed therebetween to couple the electric field to the electro-optic crystal, and that changes polarization of light incident between the one pair or electrodes according to a change of the birefringence index depending upon a strength of electric field coupled via the one pair of electrodes, the electro-optic modulation device comprising: a base portion having a top surface; a ridge portion projecting from the top surface and extending in a direction of the incident light, at least a part of the ridge portion comprising the electro-optic crystal, the ridge portion having a width equivalent to a predetermined value or less; and an insulator which covers the whole device, wherein the electrodes are formed on one pair of side faces opposed in a width direction of the ridge portion and on the whole top surface adjacent to the side faces.