Silicon optical modulators

Ever since the earliest research on optical circuits, dating back to the 1970s, there have been visions of an optical superchip (see for example(1,2)), containing a variety of integrated optical components to carry out light generation, modulation, manipulation, detection, and amplification (Fig. 1). The early work was associated with ferroelectric materials such as lithium niobate (LiNbO3), and III-V semiconductors such as gallium arsenide (GaAs) and indium phosphide (InP) based systems. LiNbO3 was interesting almost solely because of the fact that it possesses a large electro-optic coefficient(3), enabling optical modulation via the Pockels effect. Alternatively, the III-V compounds were interesting because of the relative ease of laser fabrication and the prospect of optical and electronic integration.