An optical waveguide device is provided for receiving light that has a guided mode and an unguided mode. The device comprises an optically transmissive substrate having first and second substantially opposite surfaces, an input end, and an output end. An optical waveguide region is disposed within the substrate and extends from the input to the output. A plurality of electrodes is disposed on the first surface at predetermined locations with respect to the waveguide region. The device includes a plurality of optical barriers each disposed proximate one of the first and second surfaces and positioned to block a different optical path of the unguided mode.