Hi Neal,
Thanks for your explanation.
If I understood correctly, the spatial FFT will give me an intensity as a
function of k-vector (or angle), for a given wavelength.
How do I then extract transmission and reflection spectra? Can these be
separated into the contributions from each diffracted mode?
Kind Regards,
Matt
On Wed, 20 Aug 2008, neal skinner wrote:
> Matt,
>
> Since you are asking about diffracted orders, I assume you are talking
> about a periodic structure. The concept of the spatial Fourier transform
> comes from a branch of optical science called Fourier Optics. One of the few
> textbooks I know of on the subject is *Introduction to Fourier Optics* by
> Joseph Goodman.
>
> The usual FT converts a time varying signal into a spectrum in the
> frequency domain. A spatial FT transforms a spatially varying signal or
> image at a plane into a spectrum of plane waves traveling in different
> directions or k vectors. If your image or wavefront at the reference plane
> is two dimension, then you need to compute a 2 dimensional spatial Fourier
> transform.
>
> If I was going to try this, I would use Taflove's method to compute
> the temporal FFT at each and every point in the unit cell. Then at each
> temporal frequency (wavelength), I would compute the 2 dimensional spatial
> FFT across the entire unit cell to give the diffraction pattern at each
> wavelength. You can use Matlab to compute 2-d FFTs that could be converted
> into spatial frequencies.
>
> I was actually thinking about this and going to try it a while back
> for frequency selective surfaces, but never got the time.
>
> I'm not sure if the new version of MEEP does FT's or not. If it does,
> it would save some work.
>
> I am sorry if this sound complicated, I guess it is, but I hope this
> helps.
>
> Good luck and Best regards,
>
> Neal
>
_______________________________________________
meep-discuss mailing list
[email protected]
http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
