Design and Fabrication of Crossing-Free Waveguide Routing Networks Using a Multi-Layer Polymer-Based Photonic Integration Platform

A novel 16x4 crossing-free waveguide routing network on four layers of polymer-based stacked waveguides is presented. The design combines in-plane passive waveguide devices with vertical multimode interference couplers (1x1 3D MMIs) to connect two adjacent waveguide layers. The 16x4 multilayer waveguide routing network (MWRN) is fabricated using multilayer deposition and standard UV contact lithography. A novel fabrication method of multiple waveguide layers that includes a sequence for wafer planarization steps to reduce topographies is presented. These developments lead to a reproducible multi-layer device fabricated on wafer-scale. Our technology enables a high vertical spacing of 21.6 mu m (center-to-center) between the top and bottom waveguide layers with a large waveguide-to-waveguide spacing of 7.2 mu m (center-to-center). The complex 16x4 MWRN can serve as the crossing-free waveguide routing for a 4x4 3D optical switch.