tidy3d.CustomSellmeier

class CustomSellmeier

Bases: CustomDispersiveMedium, Sellmeier

A spatially varying dispersive medium described by the Sellmeier model.

Parameters:

• name (Optional[str] = None) – Optional unique name for medium.

• frequency_range (Optional[Tuple[float, float]] = None) – [units = (Hz, Hz)]. Optional range of validity for the medium.

• allow_gain (bool = False) – Allow the medium to be active. Caution: simulations with a gain medium are unstable, and are likely to diverge.Simulations where ‘allow_gain’ is set to ‘True’ will still be charged even if diverged. Monitor data up to the divergence point will still be returned and can be useful in some cases.

• nonlinear_spec (Union[NonlinearSpec, NonlinearSusceptibility] = None) – Nonlinear spec applied on top of the base medium properties.

• modulation_spec (Optional[ModulationSpec] = None) – Modulation spec applied on top of the base medium properties.

• heat_spec (Union[FluidSpec, SolidSpec, NoneType] = None) – Specification of the medium heat properties. They are used for solving the heat equation via the HeatSimulation interface. Such simulations can be used for investigating the influence of heat propagation on the properties of optical systems. Once the temperature distribution in the system is found using HeatSimulation object, Simulation.perturbed_mediums_copy() can be used to convert mediums with perturbation models defined into spatially dependent custom mediums. Otherwise, the heat_spec does not directly affect the running of an optical Simulation.

• coeffs (Tuple[Tuple[tidy3d.components.data.data_array.SpatialDataArray, tidy3d.components.data.data_array.SpatialDataArray], ...]) – [units = (None, um^2)]. List of Sellmeier (\(B_i, C_i\)) coefficients.

• interp_method (Literal['nearest', 'linear'] = nearest) – Interpolation method to obtain permittivity values that are not supplied at the Yee grids; For grids outside the range of the supplied data, extrapolation will be applied. When the extrapolated value is smaller (greater) than the minimal (maximal) of the supplied data, the extrapolated value will take the minimal (maximal) of the supplied data.

• subpixel (bool = False) – If True and simulation’s subpixel is also True, applies subpixel averaging of the permittivity on the interface of the structure, including exterior boundary and intersection interfaces with other structures.

Notes

The frequency-dependence of the refractive index is described by:

\[n(\lambda)^2 = 1 + \sum_i \frac{B_i \lambda^2}{\lambda^2 - C_i}\]

Example

>>> x = np.linspace(-1, 1, 5)
>>> y = np.linspace(-1, 1, 6)
>>> z = np.linspace(-1, 1, 7)
>>> coords = dict(x=x, y=y, z=z)
>>> b1 = SpatialDataArray(np.random.random((5, 6, 7)), coords=coords)
>>> c1 = SpatialDataArray(np.random.random((5, 6, 7)), coords=coords)
>>> sellmeier_medium = CustomSellmeier(coeffs=[(b1,c1),])
>>> eps = sellmeier_medium.eps_model(200e12)

See also

Sellmeier

A dispersive medium described by the Sellmeier model.

Notebooks

• Fitting dispersive material models

Lectures

• Modeling dispersive material in FDTD

Attributes

Methods

eps_dataarray_freq(frequency)	Permittivity array at frequency.
from_dispersion(n, freq, dn_dwvl[, ...])	Convert n and wavelength dispersion dn_dwvl values at frequency freq to a single-pole CustomSellmeier medium.

coeffs

eps_dataarray_freq(frequency)

Permittivity array at frequency.

Parameters:

frequency (float) – Frequency to evaluate permittivity at (Hz).

Returns:

The permittivity evaluated at frequency.

Return type:

Tuple[SpatialDataArray, SpatialDataArray, SpatialDataArray]

classmethod from_dispersion(n, freq, dn_dwvl, interp_method='nearest', **kwargs)

Convert n and wavelength dispersion dn_dwvl values at frequency freq to a single-pole CustomSellmeier medium.

Parameters:

• n (SpatialDataArray) – Real part of refractive index. Must be larger than or equal to one.

• dn_dwvl (SpatialDataArray) – Derivative of the refractive index with wavelength (1/um). Must be negative.

• freq (float) – Frequency at which n and dn_dwvl are sampled.

• interp_method (InterpMethod, optional) – Interpolation method to obtain permittivity values that are not supplied at the Yee grids.

Returns:

Single-pole Sellmeier medium with the prvoided refractive index and index dispersion valuesat at the prvoided frequency.

Return type:

CustomSellmeier

__hash__()

Hash method.