Optimal design of suspended silica on-chip splitter

Photonic splitters and couplers are one of the fundamental elements in integrated optical circuits. As such, over the past decade significant research efforts have been dedicated to the development of low loss, wide bandwidth devices. While silica-based devices have clear advantages in terms of bandwidth, silicon and silicon nitride devices have lead the field in terms of ease of integration. In the present work, we provide design parameters for a novel splitter based on a suspended silica device. Unlike previous coupler devices which have smooth transition regions, the proposed device has a small defect which enables coupling across a large membrane. The designs are based on 3D FDTD models, and incorporate wavelength, refractive index and polarization dependence. The model is experimentally verified at select wavelengths from the visible through the near-IR. For comparison, we have also modeled the splitting ratio for several materials which are commonly used as waveguiding devices.