simulation subsection to include lumped elements

[weiliangjin2021]

The following code will error at the last line.

# From https://docs.flexcompute.com/projects/tidy3d/en/latest/notebooks/ModeSolver.html
# Only modification: add a 2D material
import numpy as np
import matplotlib.pylab as plt

import tidy3d as td
from tidy3d.constants import C_0
import tidy3d.web as web
from tidy3d.plugins.mode import ModeSolver

# size of simulation domain
Lx, Ly, Lz = 8, 6, 6
dl = 0.05

# waveguide information
wg_width = 1.5
wg_height = 1.0
wg_permittivity = 4.0

# automatic grid specification
grid_spec = td.GridSpec.auto(min_steps_per_wvl=20, wavelength=1.0)

resistor = td.LumpedResistor(
	center=(2,1,0),
	size=(0, 1, 1),
	name="port",
	num_grid_cells=3,
	resistance=50.0,
	voltage_axis=2,
)

sim = td.Simulation(
    size=(Lx, Ly, Lz),
    grid_spec=grid_spec,
    lumped_elements=[resistor],
    run_time=1e-20,
    boundary_spec=td.BoundarySpec.all_sides(boundary=td.Periodic()),
)

plane = td.Box(center=(0, 0, 0), size=(4, 0, 3.5))


mode_spec = td.ModeSpec(
    num_modes=1,
    target_neff=2.0,
)


mode_solver = ModeSolver(
    simulation=sim,
    plane=plane,
    mode_spec=mode_spec,
    freqs=[1e14],
)

mode_solver.reduced_simulation_copy.simulation.volumetric_structures

This is because mode solver is using a reduced simulation (

tidy3d/tidy3d/plugins/mode/mode_solver.py

Line 350 in ce64857

solver = self.reduced_simulation_copy

), which comes from

tidy3d/tidy3d/components/simulation.py

Lines 1349 to 1361 in ce64857

	def subsection(
	self,
	region: Box,
	boundary_spec: BoundarySpec = None,
	grid_spec: Union[GridSpec, Literal["identical"]] = None,
	symmetry: Tuple[Symmetry, Symmetry, Symmetry] = None,
	sources: Tuple[SourceType, ...] = None,
	monitors: Tuple[MonitorType, ...] = None,
	remove_outside_structures: bool = True,
	remove_outside_custom_mediums: bool = False,
	include_pml_cells: bool = False,
	**kwargs,
	) -> AbstractYeeGridSimulation:

. Lumped element outside the reduced simulation domain should be excluded.

[momchil-flex]

Note that in his recent PR (merged in develop) Casey introduced a try-except for the reduced simulation copy in the mode solver to avoid unexpected issues like this (something like that popped up for nonlinear materials too). This would fix this in principle but always better to fix properly? https://github.com/flexcompute/tidy3d/pull/1977/files#diff-4d80d757aca9b68f3a9557ad726b40390e2b2185302fcfbf162b1cf3e874e79cR345-R357

[weiliangjin2021]

Note that in his recent PR (merged in develop) Casey introduced a try-except for the reduced simulation copy in the mode solver to avoid unexpected issues like this (something like that popped up for nonlinear materials too). This would fix this in principle but always better to fix properly? https://github.com/flexcompute/tidy3d/pull/1977/files#diff-4d80d757aca9b68f3a9557ad726b40390e2b2185302fcfbf162b1cf3e874e79cR345-R357

Well, try-except won't catch this because reduced simulation is generated fine, but only error if simulation.volumetric_structures is called.

[weiliangjin2021]

An easy fix (but not ideal) using try-except idea is to add a line to invoke the error,

try:
solver = self.reduced_simulation_copy
solver.simulation.volumetric_structures

[momchil-flex]

Oh I see. That makes sense if there's no obvious better fix.

[weiliangjin2021]

@dmarek-flex if we can just exclude lumped element outside the reduced domain, a better fix would be:

• each lumped element has a bounds property
• Similar to

  tidy3d/tidy3d/components/simulation.py

  Line 1465 in ce64857

  new_structures = [strc for strc in self.structures if new_box.intersects(strc.geometry)]

  , exclude lumped elements that are outside.

[dmarek-flex]

@dmarek-flex if we can just exclude lumped element outside the reduced domain, a better fix would be:

• each lumped element has a bounds property
• Similar to

  tidy3d/tidy3d/components/simulation.py

  Line 1465 in ce64857

  new_structures = [strc for strc in self.structures if new_box.intersects(strc.geometry)]

  
  , exclude lumped elements that are outside.

Yes, each lumped element has an associated geometry that we can check. Shouldn't be hard