Integrated optical modulator

An integrated optical modulator for modulating optical signals in dielectric wave guides comprising a substrate having a surface and being of a material having an index of refraction n.sub.3 ;

• at least two parallel extending electrodes being disposed in spaced relationship on said surface;
• a first wave guide disposed on said surface between two of said parallel extending electrodes and extending parallel thereto, said first wave guide having an upper surface and an index of refraction n.sub.1 ;
• a dielectric, low loss film having an index of refraction n.sub.4, said film being disposed on the upper surface of the first wave guide and covering same;
• a second wave guide having an index of refraction n.sub.2, said second wave guide being disposed on said film, and a third wave guide being disposed in spaced, parallel relationship and adjacent one of said first and second wave guides, the other of said first and second wave guides having a width approximately equal to the sum of the widths of the third wave guide, said one wave guide and the space therebetween, said film having a width at least as large as the other wave guide so that the film separates the other wave guide from said one and third wave guides, said indices of refraction of the wave guides and film having a relationship of n.sub.4 <
• n.sub.1, n.sub.2, at least said one wave guide being of an electro-optical material so that an application of a potential on said electrodes changes the propagation constants of at least said one wave guide.