Integrated Photonic Topology Optimization with Nonvertical Sidewall Profiles: Applications in Lithium Niobate and Silicon

We enable density-based topology optimization (TO) to design integrated photonic devices featuring nonvertical sidewall profiles. Specifically, we demonstrate TO for fabrication processes with slanted sidewalls which are often used to enhance vertical coupling efficiency and fabrication processes with angled sidewalls which are a common feature of etching. The techniques demonstrated are readily adaptable to other etch profiles such as asymmetric or nonlinear. The enhancements are compatible with existing TO techniques, lengthscale constraints and multi-layer designs, and any dielectric materials, suiting the techniques for both academic and commercial foundry fabrications. We demonstrated the developed capabilities by designing slanted and angled silicon grating couplers and thin-film lithium niobate on insulator dual-polarization s-bends.