Enhanced electro-optic effect in amorphous hydrogenated silicon based waveguides

We report on a direct measurement of the electro-optic effect in amorphous hydrogenated silicon based waveguides. The observed phase modulation with an applied voltage shows evidence of a threshold voltage below which the electro-optic effect is weak. At high voltages the electro-optic phase modulation is nonquadratic and significantly enhanced with respect to the bulk effect in amorphous silicon. These results are explained in terms of a model which considers inhomogeneous electric fields within the silicon layer due to voltage dependent space charges.