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

A novel 16×4 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 (1×1 3D MMIs) to connect two adjacent waveguide layers. The 16×4 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 μm (center-to-center) between the top and bottom waveguide layers with a large waveguide-to-waveguide spacing of 7.2 μm (center-to-center). The complex 16×4 MWRN can serve as the crossing-free waveguide routing for a 4×4 3D optical switch.