Which information can I obtain from the mode solver?

Date	Category
2023-12-18 20:57:30	Mode Solver

Using the Tidy3D mode solver you can perform optical mode analysis and obtain information such as mode effective index (real and imaginary parts), group index, effective area, polarization fraction, and field distribution. The results are returned within a ModeSolverData object. In the following example, we print out the information of the first four waveguide modes using the method to_dataframe(). We have considered a 500 x 220 nm silicon-on-insulator (SOI) waveguide operating at 1.55 \(\mu\)m.

from tidy3d.plugins.mode import ModeSolver
from tidy3d.plugins.mode.web import run as run_mode_solver

# Define the waveguide.
waveguide = tidy3d.Structure(
    geometry=tidy3d.Box(size=(tidy3d.inf, 0.5, 0.22)),
    medium=tidy3d.Medium(permittivity=3.47**2),
)

# Build a simulation object including the waveguide.
sim = tidy3d.Simulation(
    size=(10, 2.5, 1.5),
    grid_spec=tidy3d.GridSpec.auto(min_steps_per_wvl=20, wavelength=1.55),
    structures=[waveguide],
    run_time=1e-12,
    boundary_spec=tidy3d.BoundarySpec.all_sides(boundary=tidy3d.PML()),
)

# Plane where we want to solve the modes.
plane = tidy3d.Box(center=(0, 0, 0), size=(0, 2.5, 1.5))

# Mode specification.
mode_spec = tidy3d.ModeSpec(
  num_modes=4,
  target_neff=3.47,
  group_index_step=True,
)

# Build the mode solver.
freq0 = tidy3d.C_0 / 1.55
mode_solver = ModeSolver(
  simulation=sim,
  plane=plane,
  mode_spec=mode_spec,
  freqs=[freq0],
)

# Run the server-side mode solver.
mode_data = run_mode_solver(mode_solver)

# Print out the results.
mode_data.to_dataframe()

For more details on how to set up, run, and visualize the solver results, please refer to this notebook.