> On Nov 18, 2020, at 11:13 AM, Mandy Xia <[email protected]> wrote:
> I would like to simulate an oblique incident plane wave with different
> frequencies on a periodic structure. According to a previous post
> (https://www.mail-archive.com/[email protected]/msg00691.html
> <https://www.mail-archive.com/[email protected]/msg00691.html>),
> I should conduct the simulation for each frequency separately and use a
> narrow-band source. My understanding is we can specify one periodic condition
> at a time and at a specific incident angle, only one frequency satisfies that
> condition.
If you are interested in multiple frequencies and multiple angles, then you can
use broadband analyses as described in section 4.5 of this book chapter:
https://arxiv.org/abs/1301.5366 <https://arxiv.org/abs/1301.5366>
>
> If I choose to use narrow-band sources to simulate different frequencies, I'm
> wondering if there is a way to estimate how narrow it should be because the
> simulation becomes more expensive as I keep making it narrower. Does the
> width depend on the sampling frequency I want or something else?
You don't need a narrow-band source to perform a single-frequency calculation.
You can use a broadband source (a short pulse) and then use the
Fourier-transformed fields (via dft_fields, dft_flux, etcetera) to pick out the
response at the desired frequency.
> A second question is that I found it very expensive to rerun simulations for
> different incident angles and frequencies. And I was wondering if it is
> possible to run the different incident angle and wavelength combinations
> together, where each combination satisfies the periodic boundary condition.
> For example, if my periodic boundary condition is exp(2 * pi * i * k_z * z)
> then I change the frequency and incident direction together so that
> k*sin(theta) is always k_z, where theta is the angle between the incident
> direction and the x-y plane.
Yes, see the arXiv link above.
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