# PerturbationMedium

Dispersionless medium with heat or charge perturbations. Use this model when a medium’s permittivity and conductivity depend on a Heat or Charge result. Charge response fields are part of the saved model; the editor offers this model from New Medium while editing a Heat simulation.

The medium panel separates Thermal Properties, Optical Properties, and Optical Perturbation. Additional supported medium settings are under Advanced.

# Name

name: Optional unique name for the medium. The name appears in the Mediums list and is separate from the optical and thermal properties.

# Thermal Properties

This section appears when the task group includes a Heat solver and is omitted from a standalone FDTD task.

# Medium Type

type: Selects the thermal model under Medium Type.

Type: string

Options:

  • FluidSpec: The Heat solver does not solve for temperature in regions that use this medium.
  • SolidSpec: The Heat solver uses the solid thermal model.

Default: SolidSpec for a new medium in a Heat simulation.

# Thermal Conductivity

conductivity: Thermal conductivity. This field is shown when Medium Type is SolidSpec.

Type: floating-point number

  • Unit: W/(μm·K)
  • Constraint: greater than 0
  • Required field

NOTE

The editor has no inputs for heat capacity (capacity) or density (density). When you create a medium in a Heat simulation, the editor sets capacity to 1. To set other values, use the Python interface. See Thermal Properties for the API fields.

# Optical Properties

permittivity: Relative permittivity.

  • Unit: unitless
  • Constraint: greater than or equal to 1
  • Default: 1

conductivity: Electric conductivity. The imaginary part of the complex permittivity at angular frequency omega is given by conductivity/omega.

  • Unit: S/μm
  • Constraint: greater than or equal to 0
  • Default: 0

subpixel: If True and the simulation’s subpixel setting is also True, applies subpixel averaging to the perturbed medium.

  • Type: boolean
  • Default: True

# Optical Perturbation

Enable Optical Perturbation to expose the perturbation controls. Select one of the following representations:

  • n/k (IndexPerturbation): Perturb refractive-index and extinction-coefficient values at a selected wavelength or frequency.
  • ε/σ (PermittivityPerturbation): Perturb permittivity and conductivity directly.

perturbation_spec: Selects the n/k or ε/σ representation above.

permittivity_perturbation and conductivity_perturbation: Optional ParameterPerturbation values. Each can contain a heat response, a charge response, or both.

The perturbation controls also provide a reference temperature and a valid temperature range.

# Advanced

Advanced can contain the frequency range, Allow_gain, and Space-Time Modulation. Nonlinearity Specification is not available for perturbation media.

# Appearance

Appearance settings control the medium’s face color and transparency in the model view. They do not change the optical or thermal properties.

← PerturbationPoleResidue →