tidy3d.TFSF

class TFSF

Bases: AngledFieldSource, VolumeSource

Total-field scattered-field (TFSF) source that can inject a plane wave in a finite region.

Parameters:

• name (Attribute: name) –

  Type	Optional[str]
  Default	= None
  Description	Optional name for the source.

• 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.

• source_time (Attribute: source_time) –

  Type	Union[GaussianPulse, ContinuousWave, CustomSourceTime]
  Default
  Description	Specification of the source time-dependence.

• direction (Attribute: direction) –

  Type	Literal[‘+’, ‘-‘]
  Default
  Description	Specifies propagation in the positive or negative direction of the injection axis.

• angle_theta (Attribute: angle_theta) –

  Type	float
  Default	= 0.0
  Units	rad
  Description	Polar angle of the propagation axis from the injection axis.

• angle_phi (Attribute: angle_phi) –

  Type	float
  Default	= 0.0
  Units	rad
  Description	Azimuth angle of the propagation axis in the plane orthogonal to the injection axis.

• pol_angle (Attribute: pol_angle) –

  Type	float
  Default	= 0
  Units	rad
  Description	Specifies the angle between the electric field polarization of the source and the plane defined by the injection axis and the propagation axis (rad). pol_angle=0 (default) specifies P polarization, while pol_angle=np.pi/2 specifies S polarization. At normal incidence when S and P are undefined, pol_angle=0 defines: - Ey polarization for propagation along x.- Ex polarization for propagation along y.- Ex polarization for propagation along z.

• injection_axis (Attribute: injection_axis) –

  Type	Literal[0, 1, 2]
  Default
  Description	Specifies the injection axis. The plane of incidence is defined via this injection_axis and the direction. The popagation axis is defined with respect to the injection_axis by angle_theta and angle_phi.

Notes

The TFSF source injects \(\frac{1 W}{\mu m^2}\) of power along the injection_axis. Note that in the case of angled incidence, \(\frac{1 W}{\mu m^2}\) is still injected along the source’s injection_axis, and not the propagation direction, unlike a PlaneWave source. This allows computing scattering and absorption cross-sections without the need for additional normalization.

The TFSF source allows specifying a box region into which a plane wave is injected. Fields inside this region can be interpreted as the superposition of the incident field and the scattered field due to any scatterers present in the simulation domain. The fields at the edges of the TFSF box are modified at each time step such that the incident field is cancelled out, so that all fields outside the TFSF box are scattered fields only. This is useful in scenarios where one is interested in computing scattered fields only, for example when computing scattered cross-sections of various objects.

It is important to note that when a non-uniform grid is used in the directions transverse to the injection_axis of the TFSF source, the suppression of the incident field outside the TFSF box may not be as close to zero as in the case of a uniform grid. Because of this, a warning may be issued when nonuniform grid TFSF setup is detected. In some cases, however, the accuracy may be only weakly affected, and the warnings can be ignored.

See also

Notebooks:

• Defining a total-field scattered-field (TFSF) plane wave source

• Nanoparticle Scattering: To force a uniform grid in the TFSF region and avoid the warnings, a mesh override structure can be used as illustrated here.

Attributes

injection_plane_center

Center of the injection plane.

Methods

plot([x, y, z, ax])

Plot this source.

injection_axis

property injection_plane_center

Center of the injection plane.

plot(x=None, y=None, z=None, ax=None, **patch_kwargs)

Plot this source.

__hash__()

Hash method.