# Debye

Debye defines a dispersive medium using Debye relaxation parameters.

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

The Debye model describes a delayed polarization response. In this model, dipoles do not follow the applied electric field instantly; instead, their response relaxes over a characteristic time.

The frequency dependence of the complex-valued permittivity is:

ϵ(f)=ϵ∞+∑iΔϵi1−jfτi \epsilon(f) = \epsilon_\infty + \sum_i \frac{\Delta\epsilon_i}{1 - jf\tau_i}

This maps directly to the GUI coefficients. Each row in coeffs adds one relaxation process: delta_eps controls the strength of that relaxation, tau is the relaxation time, and eps_inf is the high-frequency relative permittivity before the slower relaxations can respond. To learn more about the physical model, see Debye relaxation (opens new window).

# Name

name: Optional unique name for the medium.

# Type

type: Medium model used by this material entry.

  • Options: Debye

# Color

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

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

# General Properties

coeffs: List of Debye relaxation coefficient rows.

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

delta_eps: Relaxation strength, written as Δε in the GUI.

  • Type: float number
  • Unit: unitless
  • Required field

tau: Relaxation time, written as τ in the GUI.

  • Type: float number
  • Unit: s, ms, us, ns, ps, or other available time 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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