Silicon waveguide based splitter

A silicon waveguide based splitter is a key device for polarization diversity circuit. A bilayer waveguide structure was proposed by MIT to split the input light into its orthogonal components. It is challenging to fabricate a bilayer silicon waveguide by the conventional two-step-etching process due to precise alignment and accurate etch thickness required. In addition, the partial etched waveguide would introduce additional insertion loss due to its non-perfect surface. Here we propose a novel method to fabricate splitters with various dimensions by using selective silicon epitaxial growth to achieve bilayer structure. The performance of the splitter fabricated is evaluated through Finite-difference-time-domain simulations. The insertion loss and efficiency of the splitters obtained is experimentally investigated. The proposed approach is potentially useful for integrated photonic circuit consisting of passive waveguides and active photodetector devices.