gsim¶

Photonic FDTD and RF/microwave simulation for GDSFactory, powered by GDSFactory+.

Engine	Status and use
GDSFactory FDTD (`gsim.fdtd`)	Primary. New photonic FDTD simulations supported by its current capabilities.
Palace (`gsim.palace`)	Established. FEM simulations for RF and microwave devices.
Meep (`gsim.meep`)	Supported. Photonic workflows that are not yet available in GDSFactory FDTD.

Photonic FDTD¶

GDSFactory FDTD (gsim.fdtd) is the primary engine for new photonic simulations. Meep (gsim.meep) remains supported for capabilities not yet available in GDSFactory FDTD.

Quick start¶

import gdsfactory as gf

from gsim import fdtd

gf.gpdk.PDK.activate()
component = gf.get_component("mmi1x2")

simulation = fdtd.Simulation()
simulation.materials(background="SiO2", overrides={"si": 3.4757})
simulation.geometry(component)
simulation.source(port="o1", wavelength_span_um=0.1)

result = simulation.run(check_cache=True)
result.plot_plotly()

Start with the MMI tutorial or browse the GDSFactory FDTD API.

GDSFactory FDTD roadmap¶

Over the next six months, we plan to add:

Material dispersion
Anisotropic materials
Periodic boundary conditions
Gradients for inverse design
Feature parity and Meep migration

Meep will be deprecated only after GDSFactory FDTD reaches the required feature coverage and a documented migration path is available.

Last updated: August 2026.

Palace for RF and microwave¶

gsim.palace is the FEM engine for driven RF and microwave simulations, eigenmodes, electrostatics, and impedance extraction.

Start with the Palace CPW tutorial or browse the Palace API.

Installation¶

pip install gsim

API reference¶

GDSFactory FDTD · Meep · Palace · Common · Cloud