tidy3d.FieldProjectionKSpaceMonitor

class FieldProjectionKSpaceMonitor

Bases: AbstractFieldProjectionMonitor

Monitor that samples electromagnetic near fields in the frequency domain and projects them on an observation plane defined in k-space.

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[PositiveInt, PositiveInt, PositiveInt]
  Default	= (1, 1, 1)
  Description	Number of grid step intervals at which near fields are recorded for projection to the far field, along each direction. 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. Using values greater than 1 can help speed up server-side far field projections with minimal accuracy loss, especially in cases where it is necessary for the grid resolution to be high for the FDTD simulation, but such a high resolution is unnecessary for the purpose of projecting the recorded near fields to the far field.

• colocate (Attribute: colocate) –

  Type	Literal[True]
  Default	= True
  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.

• normal_dir (Attribute: normal_dir) –

  Type	Optional[Literal[‘+’, ‘-‘]]
  Default	= None
  Description	Direction of the surface monitor’s normal vector w.r.t. the positive x, y or z unit vectors. Must be one of '+' or '-'. Applies to surface monitors only, and defaults to '+' if not provided.

• exclude_surfaces (Attribute: exclude_surfaces) –

  Type	Optional[Tuple[Literal[‘x-’, ‘x+’, ‘y-’, ‘y+’, ‘z-’, ‘z+’], …]]
  Default	= None
  Description	Surfaces to exclude in the integration, if a volume monitor.

• custom_origin (Attribute: custom_origin) –

  Type	Optional[Tuple[float, float, float]]
  Default	= None
  Units	um
  Description	Local origin used for defining observation points. If None, uses the monitor’s center.

• far_field_approx (Attribute: far_field_approx) –

  Type	bool
  Default	= True
  Description	Whether to enable the far field approximation when projecting fields. If True, terms that decay as O(1/r^2) are ignored, as are the radial components of fields. Typically, this should be set to True only when the projection distance is much larger than the size of the device being modeled, and the projected points are in the far field of the device.

• window_size (Attribute: window_size) –

  Type	Tuple[NonNegativeFloat, NonNegativeFloat]
  Default	= (0, 0)
  Description	Size of the transition region of the windowing function used to ensure that the recorded near fields decay to zero near the edges of the monitor. The two components refer to the two tangential directions associated with each surface. For surfaces with the normal along x, the two components are (y, z). For surfaces with the normal along y, the two components are (x, z). For surfaces with the normal along z, the two components are (x, y). Each value must be between 0 and 1, inclusive, and denotes the size of the transition region over which fields are scaled to less than a thousandth of the original amplitude, relative to half the size of the monitor in that direction. A value of 0 turns windowing off in that direction, while a value of 1 indicates that the window will be applied to the entire monitor in that direction. This field is applicable for surface monitors only, and otherwise must remain (0, 0).

• medium (Attribute: medium) –

  Type	Union[Medium, AnisotropicMedium, PECMedium, PoleResidue, Sellmeier, Lorentz, Debye, Drude, FullyAnisotropicMedium, CustomMedium, CustomPoleResidue, CustomSellmeier, CustomLorentz, CustomDebye, CustomDrude, CustomAnisotropicMedium, PerturbationMedium, PerturbationPoleResidue, Medium2D]
  Default	= None
  Description	Medium through which to project fields. Generally, the fields should be projected through the same medium as the one in which this monitor is placed, and this is the default behavior when medium=None. A custom medium can be useful in some situations for advanced users, but we recommend trying to avoid using a non-default medium.

• proj_axis (Attribute: proj_axis) –

  Type	Literal[0, 1, 2]
  Default
  Description	Axis along which the observation plane is oriented.

• proj_distance (Attribute: proj_distance) –

  Type	float
  Default	= 1000000.0
  Units	um
  Description	Radial distance of the projection points from local_origin.

• ux (Attribute: ux) –

  Type	Union[Tuple[float, …], ArrayLike[dtype=float, ndim=1]]
  Default
  Description	Local x component of wave vectors on the observation plane, relative to local_origin and oriented with respect to proj_axis, normalized by (2*pi/lambda) where lambda is the wavelength associated with the background medium. Must be in the range [-1, 1].

• uy –

  Type	Union[Tuple[float, …], ArrayLike[dtype=float, ndim=1]]
  Default
  Description	Local y component of wave vectors on the observation plane, relative to local_origin and oriented with respect to proj_axis, normalized by (2*pi/lambda) where lambda is the wavelength associated with the background medium. Must be in the range [-1, 1].

Example

>>> monitor = FieldProjectionKSpaceMonitor(
...     center=(1,2,3),
...     size=(2,2,2),
...     freqs=[250e12, 300e12],
...     name='n2f_monitor',
...     custom_origin=(1,2,3),
...     proj_axis=2,
...     ux=[0.1,0.2],
...     uy=[0.3,0.4,0.5]
...     )

See also

Notebooks:

• Performing near field to far field projections

• Field projection for a zone plate

• Metalens in the visible frequency range

• Multilevel blazed diffraction grating

Attributes

Methods

reciprocal_vector_range(values)	Ensure that ux, uy are in [-1, 1].
storage_size(num_cells, tmesh)	Size of monitor storage given the number of points after discretization.

proj_axis

proj_distance

ux

uy

classmethod reciprocal_vector_range(values)

Ensure that ux, uy are in [-1, 1].

storage_size(num_cells, tmesh)

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

__hash__()

Hash method.