Advanced silicon photonic microcavities for routing, detection and lasing applications

Abstract

The theoretical background of microcavities for photonic applications has been extensively investigated in theory over the past two decades. These structures provide the ability to filter wavelength, support high-Q modes and enhance intensity within the cavities while maintaining a small device footprint. Such characteristics make these structures good candidates to optimize performance and shrink the size of devices for both linear and nonlinear optics. Recent advancements in silicon-based fabrication technology provide access to dopants for active control, material layers such as germanium and silicon nitride, and 3D-integration technologies that were previously exclusive to electronics development, leading to tremendous progress in cavity-based integrated photonic circuits. Using the silicon photonic platform developed by our group, high-performance microcavity-based structures have been demonstrated for optical signal routing, detection, and lasing applications. We first introduce partial-drop filters and present results using them to achieve a highly uniform wavelength-division-multiplexing (WDM) compatible optical multicast system. We then implement a waveguide-coupled resonant detector using a germanium layer grown on top of the silicon. In addition to having low dark current and high-speed performance, the resonant detector extends the wavelength detection range beyond 1620nm while maintaining a device radius only 4.5[mu]m. Furthermore, an easy-to-fabricate waveguide-coupled trench-based Al2O3 microcavity is presented that achieves a Q-factor on the order of 106 with a bend radius on the scale of 100[mu]m. Compact on-chip rare-earth-ion (ytterbium, erbium, thulium) doped Al2O3 lasers were then demonstrated with a sub-milliwatt lasing threshold, making trench-based cavities a suitable platform to achieve optically pumped on-chip lasers.