Capability roadmap

Capability roadmap#

The aim is not to clone Tidy3D’s web platform. It is to approach the functionality and confidence of its FDTD workflows with an open, local, accelerator-native solver.

Strong today#

  • JAX/GPU Yee stepping with reverse-mode differentiation;

  • dielectric, conductive, dispersive, anisotropic, and complex tensor media;

  • PML, PEC, PMC, periodic and Bloch boundaries;

  • plane, Gaussian, dipole, mode, and TFSF sources;

  • field, energy, phasor, Poynting, mode-overlap, and projection detectors;

  • automatic grid/boundary setup with a voxel budget, exact planar-interface alignment, and physical-thickness PML sizing;

  • primitive geometry, extruded polygons, GDS-layer helpers, and subpixel smoothing;

  • straight-waveguide, splitter, Bragg, and ring-bus forward paths;

  • reusable filtering/projection, D4 symmetry, erosion/dilation, binary validation, bounded optimization, and reverse-tape memory planning;

  • exact notebook-derived inverse-design adapters with fully binary validation; the D4 S-matrix crossing is independently confirmed within 10% but remains below 95% parity, while the other tested devices remain explicit failures rather than local-score passes;

Near-term priorities#

  1. Spectral ergonomics: standard NumPy/xarray result containers with units, frequency axes, reference-plane metadata, and normalization provenance.

  2. Mode-port robustness: reflected-port calibration, angled/bent guides, multi-port automation, and clearer propagation conventions.

  3. Reference repair: regenerate the three quarantined Tidy3D goldens under converged, reproducible settings after explicit authorization.

  4. Grid refinement: true local refinement beyond per-axis rectilinear spacing, especially around thin slabs and curved interfaces; recorder-memory planning and physical PML sizing are now automatic.

  5. Inverse-design geometry: differentiable polygon/shape controls and curvature constraints for Autograd8-class bends, plus local refinement/checkpointing for Autograd25-scale full 3D tapes.

  6. Optimizer usability: restartable state and process-corner orchestration on top of the present high-level objective loop, callbacks, continuation, fabrication constraints, and held-out binary validation.

Later FDTD coverage#

  • astigmatic/focused and custom field/current sources;

  • near-to-far and diffraction parity;

  • tabulated optical constants and multi-pole fitting;

  • resonator \(Q\) extraction and robust termination;

  • periodic/metasurface sweep helpers;

  • complex boolean geometry and STL robustness;

  • distributed-device examples and profiling.

Explicitly outside this program#

Heat and charge solvers, EME, GUI/web API replication, and unrelated multiphysics are not part of the current FDTD parity target. They should not dilute correctness work on Maxwell simulation and optimization.