OPTICAL CONTROL DEVICE AND ITS PRODUCTION

PROBLEM TO BE SOLVED: To obtain an optical control device capable of suppressing a temp. shift characteristic by forming films having the resistance lower than the resistance of a buffer layer and a substrate on part of these two layers and controlling the resistance value of the low-resistance films to a lower level. SOLUTION: Ti diffused parts 2 are formed on the surface of a Z plate LiNbO3 substrate 1 having an elector-optic effect and are used as optical waveguides. The waveguides are of a Mach-Zehnder interference type and electrodes 6 are formed via the buffer layers and the low-resistance films 4 on the branch optical waveguides. The low-resistance films 4 have plural insulation point 5 near the optical waveguides. Electric fields are imparted to the optical waveguides from the electrode 6 on the branch optical waveguides to change the phases of the guided light propagating in the respective branch optical waveguides. The branch optical waveguide are subjected to multiplexing again to cause the intensity modulation of the guided light. The resistance value of the low-resistance films 4 is controlled to a lower level in order to improve temp. stability. Further preferably, the upper limit of the resistance value of the low-resistance films 4 is disposed in order to improve the temp. stability under the conditions of the specified change rate of the temp. to lower the sheet resistance value to