Electroabsorption modulators for CMOS compatible optical interconnects in III-V and group IV materials

While electrical systems excel at information processing, photonics is useful in systems for high-bandwidth, low-loss signal transmission. As photonics technology has become increasingly widespread and has been deployed at shorter distance scales than traditional long-haul networks, it has become important to efficiently integrate photonics components with electrical integrated circuits. Optoelectronic modulators used as transmitters are an important class of device for use in optical interconnects.; Many optoelectronic modulator designs use waveguides. Coupling light into waveguides requires a difficult alignment step. This dissertation will describe a number of optoelectronic modulators that do not have the tight alignment constraints associated with waveguide-based modulators. The eased alignment constraints may be important for the practical manufacturing and packaging of systems using optical interconnects.; Most currently deployed photonics technologies also use substrates other than silicon and materials incompatible with CMOS manufacturing. Recently we discovered a strong quantum-confined Stark effect in Ge/SiGe quantum well structures that can be used to create efficient optoelectronic modulators on silicon substrates. Optoelectronic modulators using this technology can be fabricated with conventional CMOS foundry processes, possibly on the same chips as CMOS circuits.; In this dissertation, an optical interconnect operating in the C-band will be presented. We believe this is the first such device employing an optical transmitter flip-chip bonded to silicon CMOS. A number of novel modulators will be presented, which are fabricated on silicon substrates, and employ Ge/SiGe quantum well structures. These modulators include a novel architecture known as the side-entry modulator, which is designed for monolithic integration with electronics. One side-entry modulator achieved over 3 dB of contrast in the telecommunications C-band for a voltage swing of 1V. Such a device is compatible with both the voltage swing of modern CMOS circuits, and long-distance telecommunications technologies including low-loss optical fiber and erbium-doped fiber amplifiers.