tidy3d.Absorber

class Absorber

Bases: AbsorberSpec

Specifies an adiabatic absorber along a single dimension.

Parameters:

• name (Attribute: name) –

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

• num_layers (Attribute: num_layers) –

  Type	NonNegativeInt
  Default	= 40
  Description	Number of layers of absorber to add to + and - boundaries.

• parameters (Attribute: parameters) –

  Type	AbsorberParams
  Default	= AbsorberParams(sigma_order3, sigma_min0.0, sigma_max6.4, type’AbsorberParams’)
  Description	Adiabatic absorber parameters.

Notes

This absorber is well-suited for dispersive materials intersecting with absorbing edges of the simulation at the expense of more layers.

Usage Caveats

Using absorber boundary is often a good remedy to resolve divergence issues related to PML. The adiabatic absorber is a multilayer system with gradually increasing conductivity. The absorber usually has a larger undesired reflection compared to PML. In practice, this small difference rarely matters, but is important to understand for simulations that require high accuracy.

There are two possible sources for the reflection from absorbers. The first, and more common one, is that the ramping up of the conductivity is not sufficiently slow, which can be remedied by increasing the number of absorber layers (40 by default). The second one is that the absorption is not high enough, such that the light reaches the PEC boundary at the end of the Absorber, travels back through it, and is still not fully attenuated before re-entering the simulation region. If this is the case, increasing the maximum conductivity AbsorberParams can help. In both cases, changing the order of the scaling of the conductivity (tidy3d.AbsorberParams.sigma_order) can also have an effect, but this is a more advanced setting that we typically do not recommend modifying.

Example

>>> pml = Absorber(num_layers=40)

See also

PML:

A standard PML along a single dimension.

Notebooks:

• How to troubleshoot a diverged FDTD simulation

Attributes

Methods

num_layers

parameters

__hash__()

Hash method.