A modulator includes an electro-optical substrate and a first and second waveguide formed of a doped semiconductor material positioned on a surface of an electro-optical substrate forming a slot therebetween. A doping level of the semiconductor material being chosen to make the first and second waveguide conductive. A dielectric material is positioned in the slot which increases confinement of both an optical field and an electrical field inside the slot. A refractive index of the semiconductor material and a refractive index of the dielectric material positioned in the slot being chosen to reduce the Vπ·L product of the modulator.