GeSi photonics for telecommunication applications

We experimentally and theoretically investigate GeSi-based photonics for future on-chip optical interconnect on bulk Silicon substrates with dense wavelength division multiplexing (WDM) system. We experimentally show that Ge-rich Si1-xGex can be used as both a passive low loss waveguide and a substrate to facilitate low-temperature epitaxial growth of Ge-based active devices working at low optical loss wavelength of Ge-rich Si1-xGex waveguides. We also theoretically discussed the possibilities to realize a compact passive component based on Ge-rich Si1-xGex material system on bulk Si wafer. From simulation the system based on Ge-rich Si1-xGex waveguide and the Si1-yGey (y < x) lower cladding layer is good enough to ensure compactness of important on-chip photonic components including passive waveguide and GeSi-based array waveguide grating (AWG). The small refractive index contrast between Ge-rich Si1-xGex waveguide and the Si1-yGey lower cladding layer potentially avoid the polarization dependent loss and detrimental fabrication tolerance of WDM system. Our studies show that GeSi-based photonics could uniquely provide both passive and active functionalities for dense WDM system.