Abstract: A waveguide device is provided. The device comprises a semiconductor waveguide structure and at least one charge storing structure. Said at least one charge storing structure is configured to apply selected electric field on the semiconductor waveguide structure to thereby vary refractive index within said semiconductor waveguide structure. Wherein the charge storing structure comprises a charge trapping layer configured for storing charge carriers configured for selectively generating constant electric field of a predetermined magnitude. The device may be used in optical resonators, interferometer for optical and optoelectronic applications, capable of desirably varying refractive index within the waveguide structure.