# Drude

Drude defines a dispersive medium using Drude model parameters.

This object corresponds to tidy3d.Drude (opens new window).

The Drude model describes free carriers in a conductive material. The carriers are accelerated by the electric field and damped by scattering, so the material response is strong at low frequency and becomes weaker at high frequency.

The frequency dependence of the complex-valued permittivity is:

ϵ(f)=ϵ∞−∑ifi2f2+jfδi \epsilon(f) = \epsilon_\infty - \sum_i \frac{f_i^2}{f^2 + jf\delta_i}

This maps directly to the GUI coefficients. Each row in coeffs adds one free-carrier contribution: f is the plasma frequency, delta is the damping or scattering rate, and eps_inf is the background relative permittivity from faster responses not captured by the Drude terms. To learn more about the physical model, see the Drude model (opens new window).

# Name

name: Optional unique name for the medium.

# Type

type: Medium model used by this material entry.

  • Options: Drude

# Color

color: Display color used for the medium in the GUI.

  • Type: color
  • Default: automatically assigned by the GUI

# General Properties

coeffs: List of Drude coefficient rows.

  • Type: list of two-value coefficient rows
  • Required field

f: Plasma frequency.

  • Type: float number
  • Unit: Hz, kHz, MHz, GHz, THz, or other available frequency unit
  • Required field

delta: Damping rate, written as δ in the GUI.

  • Type: float number
  • Unit: Hz, kHz, MHz, GHz, THz, or other available frequency unit
  • Constraint: greater than 0
  • Required field

eps_inf: Relative permittivity at infinite frequency.

  • Type: float number
  • Unit: unitless
  • Constraint: greater than 0
  • Default: 1

# Advanced

set_from_global_frequency: Toggle whether the frequency range is set from the Global Settings frequency range.

  • Options:
    • True: Use the global frequency range and disable manual frequency range inputs.
    • False: Manually set frequency_range.

frequency_range: Optional range of validity for the medium.

  • Type: two float numbers
  • Unit: Hz, kHz, MHz, GHz, THz, or other available frequency unit
  • Default: None

allow_gain: Toggle whether the medium is allowed to be active.

  • Options: True/False
  • Default: False

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