Versatile Silicon-Oxynitride Planar Lightwave Circuits for Interconnect Applications

Low-cost silica (SiO2) on silicon integrated planar lightwave components for applications in interconnect and optical networks have been developed. Using silicon-oxynitride (SiON) as the optically guiding core layer, a great flexibility in the design of planar optical waveguide structures is obtained as the refractive index of SiON can be varied by changing its nitrogen content. This enables the fabrication of weakly guiding waveguides with an optical mode matched to standard single mode fibers as well as more strongly guiding waveguides for compact integrated lightwave circuits. This technology can also be used as a silicon motherboard for advanced hybrid packages for optical interconnects. As an example, with a refractive index of the SiON core layer of 1.50, waveguide structures with bending radii of 1.5 mm can be achieved. The strength of this planar waveguide technology is illustrated by the example of a thermo-optically tunable space switch that can be used either as a single 1-to-8 switch or multiple parallel 1-to-4, 1-to-3 or 1-to-2 switches.