Integrated Ultrafast Nonlinear Optical Devices in Silicon

Silicon-on-insulator (SOI) provides an intriguing system for developing massively integrated optics. By leveraging the processes and systems developed for electronics fabrication, it is possible to make highly repeatable devices where complexity can be scaled up through the use of wafer-scale batch fabrication. Because the mode concentration in silicon waveguides is two orders of magnitude higher than in fibers, it is possible to construct very compact nonlinear optical devices within this system, enabling the miniaturization and integration of ultrafast nonlinear devices. We have developed a library of devices, including both dielectric and plasmonic waveguides, as well as resonators, splitters, and a variety of other basic optical components. Using these components to construct integrated devices of moderate complexity, we have demonstrated Pockels’ Effect-based ring modulators, optical rectification-based detectors, four-wave mixing devices, and ultrafast intensity modulators, which operate at speeds in excess of 2 Terahertz. By integrating optical polymers through evanescent coupling to high-mode-confinement silicon waveguides, the effective nonlinearity of the waveguides can be greatly increased. The combination of high mode confinement, multiple integrated optical components, and high nonlinearity produces all-optical ultrafast devices operating at power levels compatible with modern continuous-wave telecommunication systems. Although far from commercial modulator standards in terms of extinction, these modulator devices are a first step toward large scale integrated ultrafast optical logic in silicon, and are two orders of magnitude faster than existing freecarrier-based silicon devices.