tidy3d.DiffractionMonitor

tidy3d.DiffractionMonitor#

class DiffractionMonitor[source]#

Bases: PlanarMonitor, FreqMonitor

Monitor that uses a 2D Fourier transform to compute the diffraction amplitudes and efficiency for allowed diffraction orders.

Parameters:

  • attrs (dict = {}) – Dictionary storing arbitrary metadata for a Tidy3D object. This dictionary can be freely used by the user for storing data without affecting the operation of Tidy3D as it is not used internally. Note that, unlike regular Tidy3D fields, attrs are mutable. For example, the following is allowed for setting an attr obj.attrs['foo'] = bar. Also note that Tidy3D will raise a TypeError if attrs contain objects that can not be serialized. One can check if attrs are serializable by calling obj.json().

  • center (Union[tuple[Union[float, autograd.tracer.Box], Union[float, autograd.tracer.Box], Union[float, autograd.tracer.Box]], Box] = (0.0, 0.0, 0.0)) – [units = um]. Center of object in x, y, and z.

  • size (Union[tuple[Union[pydantic.v1.types.NonNegativeFloat, autograd.tracer.Box], Union[pydantic.v1.types.NonNegativeFloat, autograd.tracer.Box], Union[pydantic.v1.types.NonNegativeFloat, autograd.tracer.Box]], Box]) – [units = um]. Size in x, y, and z directions.

  • name (ConstrainedStrValue) – Unique name for monitor.

  • interval_space (Tuple[Literal[1], Literal[1], Literal[1]] = (1, 1, 1)) – 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 (Literal[False] = False) – Defines whether fields are colocated to grid cell boundaries (i.e. to the primal grid). Can be toggled for field recording monitors and is hard-coded for other monitors depending on their specific function.

  • freqs (Union[tuple[float, ...], ArrayLike[dtype=float, ndim=1]]) – [units = Hz]. Array or list of frequencies stored by the field monitor.

  • apodization (ApodizationSpec = ApodizationSpec(attrs={}, start=None, end=None, width=None, type='ApodizationSpec')) – 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 (Literal['+', '-'] = +) – Direction of the surface monitor’s normal vector w.r.t. the positive x, y or z unit vectors. Must be one of '+' or '-'. Defaults to '+' if not provided.

Note

The diffraction data are separated into S and P polarizations. At normal incidence when S and P are undefined, P(S) corresponds to Ey``(``Ez) polarization for monitor normal to x, P(S) corresponds to Ex``(``Ez) polarization for monitor normal to y, and P(S) corresponds to Ex``(``Ey) polarization for monitor normal to z.

Note

The power amplitudes per polarization and diffraction order, and correspondingly the power per diffraction order, correspond to the power carried by each diffraction order in the monitor normal direction. They are not to be confused with power carried by plane waves in the propagation direction of each diffraction order, which can be obtained from the spherical-coordinate fields which are also stored. The power definition is such that the grating efficiency is the recorded power over the input source power, and the direct sum over the power in all orders should equal the total power flowing through the monitor.

Example

>>> monitor = DiffractionMonitor(
...     center=(1,2,3),
...     size=(inf,inf,0),
...     freqs=[250e12, 300e12],
...     name='diffraction_monitor',
...     normal_dir='+',
...     )

See also

Notebooks

Attributes

attrs

Methods

diffraction_monitor_size(val)

Ensure that the monitor is infinite in the transverse direction.

storage_size(num_cells, tmesh)

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

Inherited Common Usage

normal_dir#
colocate#
classmethod diffraction_monitor_size(val)[source]#

Ensure that the monitor is infinite in the transverse direction.

storage_size(num_cells, tmesh)[source]#

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

__hash__()#

Hash method.