Guide/antiguide optical intensity modulator

An electrorefractive index-controllable guide/antiguide optical intensity modulator has been created and characterized. The operating mechanism, beam propagation method simulation, device design and fabrication, and calculated and experimental results of this guide/antiguide modulator are given. The operational principle of the modulator is based on the field-induced waveguide (FIG) concept; that is, electric-field-induced refractive index changes cause the waveguide to be turned on and off electrically. The modulator is formed with a central narrow FIG electrode sandwiched between two antiguide electrodes. The electrooptic effects, along with carrier effects, have been exploited to adjust the refractive index under the guide and adjacent antiguide electrodes by changing reverse biases applied to them. The modulation is determined mainly by changing the lateral refractive index profiles. In the on state, a waveguide is formed under the central electrode, and the input light propagates along this waveguide. To realize the best off state, an antiguide situation is created that causes the light to diffract out of the central guide rapidly. An on/off ratio larger than 23 dB, a propagation loss 1 dB, and a record optical bandwidth from 1.0 to 1.55 m have been obtained for this modulator.