On Wed, 28 Mar 2007, Markus Testorf wrote:
I think your response to Matt demands a follow up. Matt's problem (as well as ours) involves periodic boundaries. In our simulations we clearly see that a periodically continued line source only produces a plane wave (CW) without artifacts for specific combinations of wavelength and k vector. These coincide very well with what we would naively expect from periodic boundaries, i.e. sin(prop. angle) = n lambda/period. To us this is an indication that the periodic BC are implemented without correcting for phase mismatch at the boundaries in order to compensate for this problem, and we are unaware of any way to invoke such a correction.
Each frequency component produces a plane wave at a specific angle, with a different angle for each frequency component. Therefore if you put in a pulse, you get a superposition of waves from each frequency & angle, and the field will "look" like a mess. However, if you were to take a Fourier transform of the field in time, each Fourier component would again be a nice wave at one angle.
This is precisely what the flux-spectrum feature in Meep does. It takes the Fourier transform of the fields in time, and then computes the flux of the Fourier components. So the flux at each frequency corresponds to a source at a well-defined angle.
Steven _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
