GUIDE ANTIGUIDE OPTICAL-INTENSITY MODULATOR

An electrorefractive index-controllable guide/antiguide optical intens ity modulator has been created and characterized. The operating mechan ism, beam propagation method simulation, device design and fabrication , and calculated and experimental results of this guide/antiguide modu lator are given. The operational principle of the modulator is based o n the field-induced waveguide (FIG) concept; that is, electric-field-i nduced refractive index changes cause the waveguide to be turned on an d off electrically. The modulator is formed with a central narrow FIG electrode sandwiched between two antiguide electrodes. The electroopti c effects, along with carrier effects, have been exploited to adjust t he refractive index under the guide and adjacent antiguide electrodes by changing reverse biases applied to them. The modulation is determin ed mainly by changing the lateral refractive index profiles. In the on state, a waveguide is formed under the central electrode, and the inp ut light propagates along this waveguide. To realize the best off stat e, 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 approximately 1 dB, and a record optical bandwidth from 1.0 to 1.55 mum have been obtained for this modulator.