tidy3d.Sellmeier

class Sellmeier

Bases: DispersiveMedium

A dispersive medium described by the Sellmeier model.

Parameters:

• name (Attribute: name) –

  Type	Optional[str]
  Default	= None
  Description	Optional unique name for medium.

• frequency_range (Attribute: frequency_range) –

  Type	Optional[Tuple[float, float]]
  Default	= None
  Units	(Hz, Hz)
  Description	Optional range of validity for the medium.

• allow_gain (Attribute: allow_gain) –

  Type	bool
  Default	= False
  Description	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 (Attribute: nonlinear_spec) –

  Type	Union[NonlinearSpec, NonlinearSusceptibility]
  Default	= None
  Description	Nonlinear spec applied on top of the base medium properties.

• modulation_spec (Attribute: modulation_spec) –

  Type	Optional[ModulationSpec]
  Default	= None
  Description	Modulation spec applied on top of the base medium properties.

• heat_spec (Attribute: heat_spec) –

  Type	Union[FluidSpec, SolidSpec, NoneType]
  Default	= None
  Description	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 (Attribute: coeffs) –

  Type	Tuple[Tuple[float, pydantic.v1.types.PositiveFloat], …]
  Default
  Units	(None, um^2)
  Description	List of Sellmeier (\(B_i, C_i\)) coefficients.

Notes

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

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

For lossless, weakly dispersive materials, the best way to incorporate the dispersion without doing complicated fits and without slowing the simulation down significantly is to provide the value of the refractive index dispersion \(\frac{dn}{d\lambda}\) in tidy3d.Sellmeier.from_dispersion(). The value is assumed to be at the central frequency or wavelength (whichever is provided), and a one-pole model for the material is generated.

Example

>>> sellmeier_medium = Sellmeier(coeffs=[(1,2), (3,4)])
>>> eps = sellmeier_medium.eps_model(200e12)

See also

CustomSellmeier

A spatially varying dispersive medium described by the Sellmeier model.

Notebooks

• Fitting dispersive material models

Lectures

• Modeling dispersive material in FDTD

Attributes

Methods

eps_model(frequency)	Complex-valued permittivity as a function of frequency.
from_dispersion(n, freq[, dn_dwvl])	Convert n and wavelength dispersion dn_dwvl values at frequency freq to a single-pole Sellmeier medium.

coeffs

eps_model(frequency)

Complex-valued permittivity as a function of frequency.

classmethod from_dispersion(n, freq, dn_dwvl=0, **kwargs)

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

Parameters:

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

• dn_dwvl (float = 0) – Derivative of the refractive index with wavelength (1/um). Must be negative.

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

Returns:

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

Return type:

Sellmeier

__hash__()

Hash method.