Comparison of Lumerical FDTD and Tidy3D for three-dimensional FDTD simulations of passive silicon photonic components

We benchmark Lumerical FDTD and Tidy3D for 3D simulations of passive silicon photonic components on the silicon-on-insulator (SOI) platform. Six devices—including an MMI, directional coupler, waveguide crossing, mode converter, polarization splitter rotator, and ring resonator—are simulated under matched conditions using geometries from the generic process design kit (PDK) from GDSFactory. Our study emphasizes comparing simulation accuracy across both solvers, alongside an analysis of runtime and broadband behavior over varying resolutions and bandwidths. Results show that both solvers are reliable with minimal discrepancies.