InP-based quantum wells for electro-optic waveguide circuits

The author discusses some of the device issues that arise when InP-based quantum wells (QWs) are incorporated in guided-wave photonic integrated circuits (PICs). By operating at wavelengths close to the bandgap, enhanced electrooptic effects allow QW waveguide switches and modulators to have sizes that are significantly smaller than those in bulk semiconductors. Compactness is an advantage for monolithic integration with other components, for high-speed operation, and for lowering the unit cost by increasing the number of devices per wafer. However for QW devices to be useful in real optical systems, the negative implications of using near-bandedge phenomena must be confronted. These may include high propagation loss, limited optical bandwidth, and polarization-dependence. For manufacture of QW PICs the number of processing steps and their complexity must be reduced. These issues were examined and it was found that some can be successfully addressed through materials science and bandgap engineering