Abstract: An electro-optical light wave modulator is a waveguide constituted by a thin electro-optic material layer on which conductive clads are deposited and supported by a substrate. The refractive index of the thin layer is larger than that of air and that of the substrate material, so that vertical guiding is inherently ensured.The conductive clads form a divergent arrangement which opens towards a light input. At the device inlet, the distance between the conductive clads is large enough for guiding one or several light wave modes. At the device outlet, the corresponding distance is too small for guiding any mode when no difference of voltage is applied to the clads. When the voltage difference between the two clads reaches a certain value, the resulting electric field enable the device outlet to guide one or several modes, depending on such a voltage value. By varying the voltage difference, it is possible to modulate light which is outgoing from the device outlet.