Lightsmith

The open photonics suite — GPU-native, differentiable, and built for AI agents.

Describe a photonics problem once, as typed JSON, and solve it with the method that fits: from nanoparticles and thin films to metasurfaces, waveguides, photonic crystals, devices and circuits. Every result comes back in the same units and conventions, with provenance, so methods can be cross-checked directly. Many solvers run on GPU and can be differentiated, which is what powers inverse design.

Documentation: https://lightsmith-photonics.github.io/lightsmith/

Status: pre-alpha (v0.1). Validation numbers for every solver are in tests/ and in the technical report (lightsmith-paper repository).

Install

uv add lightsmith                    # CPU
uv add "lightsmith[gpu]"             # + PyTorch for GPU solvers
uv add "lightsmith[mcp]"             # + MCP server for AI agents
uv add "lightsmith[tmatrix]"         # + treams T-matrix backend
uv add "lightsmith[layout]"          # + gdsfactory import (Python >= 3.11)

From a clone (pulls CUDA 12.8 PyTorch wheels on Windows/Linux):

uv sync --extra gpu --extra mcp
uv run lightsmith doctor

Quick start

import lightsmith as ls

sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=40),
                           material=ls.LibraryMaterial(name="Au"))],   # Johnson & Christy
    medium_index=1.33,
    wavelengths=ls.WavelengthRange(start_nm=400, stop_nm=800, num=81),
)

ls.estimate(sim, method="fdtd", device="gpu")   # grid, steps, memory; never solves
res = ls.solve(sim)                             # auto -> exact Mie for a sphere
cmp = ls.compare(sim, ["mie", "dda", "fdtd"])   # cross-check methods

The same from the shell, JSON in and out:

uv run lightsmith solve examples/drude_sphere.json --method dda --device gpu

Problems and solvers

lightsmith backends lists what is installed. Materials: bundled CC0 datasets (Au, Ag, Al, Cu, Si, SiO2, TiO2, water) from the refractiveindex.info database, online fetch of any entry, and passive Drude–Lorentz fitting for time-domain solvers.

GPL-licensed solvers live in separate plugin packages discovered through the lightsmith.backends entry point (lightsmith-adda, lightsmith-scattnlay), keeping this core MIT.

Conventions

• Lengths in nm; wavelengths are vacuum wavelengths.
• Time dependence exp(-iωt): absorbing materials have Im(ε) > 0.
• Scattering cross sections in nm²; efficiencies use the volume-equivalent radius, Q = C / (π r_eq²).

For AI agents

• lightsmith schema prints the JSON Schema of every problem kind.
• Every CLI command prints JSON; failures print {"error", "message"} to stderr with exit code 1.
• lightsmith-mcp serves get_schema, list_backends, check_environment, estimate, solve and compare.
• See AGENTS.md and llms.txt.

Licence

MIT. Backends keep their own licences; cite the ones you use (Result.provenance, lightsmith backends).

Related repositories

Lightsmith is split across sibling repositories: