Method __init__

python/simulation.py:222–286

+ **`thickness` [ `number` ]** — The spatial thickness of the PML layer which extends from the boundary towards the *inside* of the cell. The thinner it is, the more numerical reflections become a problem. No default value. + **`direction` [ `direction` constant

(
        self,
        thickness: float = None,
        direction: int = mp.ALL,
        side: int = mp.ALL,
        R_asymptotic: float = 1e-15,
        mean_stretch: float = 1.0,
        pml_profile: Callable[[float], float] = DefaultPMLProfile,
    )

    """

    def __init__(
        self,
        thickness: float = None,
        direction: int = mp.ALL,
        side: int = mp.ALL,
        R_asymptotic: float = 1e-15,
        mean_stretch: float = 1.0,
        pml_profile: Callable[[float], float] = DefaultPMLProfile,
    ):
        """
        + **`thickness` [ `number` ]** — The spatial thickness of the PML layer which
          extends from the boundary towards the *inside* of the cell. The thinner it is,
          the more numerical reflections become a problem. No default value.

        + **`direction` [ `direction` constant ]** — Specify the direction of the
          boundaries to put the PML layers next to. e.g. if `X`, then specifies PML on the
          $\\pm x$ boundaries (depending on the value of `side`, below). Default is the
          special value `ALL`, which puts PML layers on the boundaries in all directions.

        + **`side` [ `side` constant ]** — Specify which side, `Low` or `High` of the
          boundary or boundaries to put PML on. e.g. if side is `Low` and direction is
          `meep.X`, then a PML layer is added to the $-x$ boundary. Default is the special
          value `meep.ALL`, which puts PML layers on both sides.

        + **`R_asymptotic` [ `number` ]** — The asymptotic reflection in the limit of
          infinite resolution or infinite PML thickness, for reflections from air (an
          upper bound for other media with index > 1). For a finite resolution or
          thickness, the reflection will be *much larger*, due to the discretization of
          Maxwell&#x27;s equation. Default value is 10<sup>−15</sup>, which should suffice for
          most purposes. You want to set this to be small enough so that waves propagating
          within the PML are attenuated sufficiently, but making `R_asymptotic` too small
          will increase the numerical reflection due to discretization.

        + **`pml_profile` [ `function` ]** — By default, Meep turns on the PML conductivity
          quadratically within the PML layer &mdash; one doesn&#x27;t want to turn it on
          suddenly, because that exacerbates reflections due to the discretization. More
          generally, with `pml_profile` one can specify an arbitrary PML "profile"
          function $f(u)$ that determines the shape of the PML absorption profile up to an
          overall constant factor. *u* goes from 0 to 1 at the start and end of the PML,
          and the default is $f(u) = u^2$. In some cases where a very thick PML is
          required, such as in a periodic medium (where there is technically no such thing
          as a true PML, only a pseudo-PML), it can be advantageous to turn on the PML
          absorption more smoothly. See [Optics Express, Vol. 16, pp. 11376-92
          (2008)](http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-15-11376). For
          example, one can use a cubic profile $f(u) = u^3$ by specifying
          `pml_profile=lambda u: u*u*u`.
        """
        if thickness is None:
            raise ValueError("PML thickness must be specified.")

        self.thickness = thickness
        self.direction = direction
        self.side = side
        self.R_asymptotic = R_asymptotic
        self.mean_stretch = mean_stretch
        self.pml_profile = pml_profile

        if direction == mp.ALL and side == mp.ALL: