Class ContinuousSource

python/source.py:174–253

A continuous-wave (CW) source is proportional to $\\exp(-i\\omega t)$, possibly with a smooth (exponential/tanh) turn-on/turn-off. In practice, the CW source [never produces an exact single-frequency response](FAQ.md#why-doesnt-the-continuous-wave-cw-source-produce-an-exact-single-f

class ContinuousSource(SourceTime):
    """
    A continuous-wave (CW) source is proportional to $\\exp(-i\\omega t)$, possibly with a
    smooth (exponential/tanh) turn-on/turn-off. In practice, the CW source [never produces
    an exact single-frequency
    response](FAQ.md#why-doesnt-the-continuous-wave-cw-source-produce-an-exact-single-frequency-response).
    """

    def __init__(
        self,
        frequency=None,
        start_time=0,
        end_time=1.0e20,
        width=0,
        fwidth=float("inf"),
        cutoff=None,
        slowness=3.0,
        wavelength=None,
        is_integrated=False,
        **kwargs,
    ):
        """
        Construct a `ContinuousSource`.

        + **`frequency` [`number`]** — The frequency *f* in units of $c$/distance or ω in
          units of 2π$c$/distance. See [Units](Introduction.md#units-in-meep). No default
          value. You can instead specify `wavelength=x` or `period=x`, which are both a
          synonym for `frequency=1/x`; i.e. 1/ω in these units is the vacuum wavelength or
          the temporal period.

        + **`start_time` [`number`]** — The starting time for the source. Default is 0
          (turn on at $t=0$).

        + **`end_time` [`number`]** — The end time for the source. Default is
          10<sup>20</sup> (never turn off).

        + **`width` [`number`]** — Roughly, the temporal width of the smoothing
          (technically, the inverse of the exponential rate at which the current turns off
          and on). Default is 0 (no smoothing). You can instead specify `fwidth=x`, which
          is a synonym for `width=1/x` (i.e. the frequency width is proportional to the
          inverse of the temporal width).

        + **`slowness` [`number`]** — Controls how far into the exponential tail of the
          tanh function the source turns on. Default is 3.0. A larger value means that the
          source turns on more gradually at the beginning. For a detailed explanation
          of the effects of `width` and `slowness` on the time profile of the source,
          see [here](FAQ.md##why-doesnt-the-continuous-wave-cw-source-produce-an-exact-single-frequency-response).

        + **`is_integrated` [`boolean`]** — If `True`, the source is the integral of the
          current (the [dipole
          moment](https://en.wikipedia.org/wiki/Electric_dipole_moment)) which oscillates
          but does not increase for a sinusoidal current. In practice, there is little
          difference between integrated and non-integrated sources *except* for
          [planewaves extending into
          PML](Perfectly_Matched_Layer.md#planewave-sources-extending-into-pml). Default
          is `False`.
        """