tidy3d.ModeMonitor

class ModeMonitor

Bases: AbstractModeMonitor

Monitor that records amplitudes from modal decomposition of fields on plane.

Parameters:

• center (Attribute: center) –

  Type	Tuple[float, float, float]
  Default	= (0.0, 0.0, 0.0)
  Units	um
  Description	Center of object in x, y, and z.

• size (Attribute: size) –

  Type	Tuple[NonNegativeFloat, NonNegativeFloat, NonNegativeFloat]
  Default
  Units	um
  Description	Size in x, y, and z directions.

• name (Attribute: name) –

  Type	ConstrainedStrValue
  Default
  Description	Unique name for monitor.

• interval_space (Attribute: interval_space) –

  Type	Tuple[Literal[1], Literal[1], Literal[1]]
  Default	= (1, 1, 1)
  Description	Number of grid step intervals between monitor recordings. If equal to 1, there will be no downsampling. If greater than 1, the step will be applied, but the first and last point of the monitor grid are always included. Not all monitors support values different from 1.

• colocate (Attribute: colocate) –

  Type	Literal[False]
  Default	= False
  Description	Defines whether fields are colocated to grid cell boundaries (i.e. to the primal grid) on-the-fly during a solver run. Can be toggled for field recording monitors and is hard-coded for other monitors depending on their specific function.

• freqs (Attribute: freqs) –

  Type	Union[Tuple[float, …], ArrayLike[dtype=float, ndim=1]]
  Default
  Units	Hz
  Description	Array or list of frequencies stored by the field monitor.

• apodization (Attribute: apodization) –

  Type	ApodizationSpec
  Default	= ApodizationSpec(startNone, endNone, widthNone, type’ApodizationSpec’)
  Description	Sets parameters of (optional) apodization. Apodization applies a windowing function to the Fourier transform of the time-domain fields into frequency-domain ones, and can be used to truncate the beginning and/or end of the time signal, for example to eliminate the source pulse when studying the eigenmodes of a system. Note: apodization affects the normalization of the frequency-domain fields.

• mode_spec (Attribute: mode_spec) –

  Type	ModeSpec
  Default
  Description	Parameters to feed to mode solver which determine modes measured by monitor.

Notes

The fields recorded by frequency monitors (and hence also mode monitors) are automatically normalized by the power amplitude spectrum of the source. For multiple sources, the user can select which source to use for the normalization too.

We can also use the mode amplitudes recorded in the mode monitor to reveal the decomposition of the radiated power into forward- and backward-propagating modes, respectively.

Example

>>> mode_spec = ModeSpec(num_modes=3)
>>> monitor = ModeMonitor(
...     center=(1,2,3),
...     size=(2,2,0),
...     freqs=[200e12, 210e12],
...     mode_spec=mode_spec,
...     name='mode_monitor')

See also

Notebooks:

• ModalSourcesMonitors

Attributes

Methods

storage_size(num_cells, tmesh)

Size of monitor storage given the number of points after discretization.

colocate

storage_size(num_cells, tmesh)

Size of monitor storage given the number of points after discretization.

__hash__()

Hash method.