Perhaps I'm not understanding, but I don't think I'm (necessarily) creating a supercell in my construction of the problem. For concreteness let's assume the simulation is set up as follows: X/Y each span [-5,5] um. If I place disks at (-2.5,0) and (2.5,0) I have definitely created a supercell. However, if I place them at (-1,0) and (2.5, 2.3) I don't see how that creates a supercell. Only positions that have distances between them that are integer factors of the total cell size will produce supercells (which, in general, is unlikely). It is a completely reasonable concern that I'll accidentally create a supercell and that will produce errors, but doesn't approach 2 naturally avoid that outcome? Shifting the produced fields would (perhaps naively) seem to me to be the same as shifting the source as suggested in the book referenced in that FAQ. Or, do I need to both spatially- and phase-shift the fields produced from each disk individually? It wouldn't be hard to multiply the fields by a phase-factor after circularly shifting them.
-Ben On Tue, Apr 23, 2019 at 1:02 PM Ardavan Oskooi <ardavan.osk...@gmail.com> wrote: > On 4/23/19 10:32, Ben Cerjan wrote: > > > The interference effects should be captured by the (complex) fields -- > > they contain both amplitude and phase information as a function of > > position (in analogy to the Huygens-Fresnel principle). In my head > > this should work, as a linear superposition of the complex fields will > > produce the total field. > > > > As to your second point, I'm asserting that the two disks are > > sufficiently far apart that they do not couple in the near-field (a > > few hundred nm in the visible, for example). You are absolutely > > correct that if the disks are too close there is no other choice but > > to redo the full simulation. > > Two (non-interacting) disks in a single "unit cell" is actually a > supercell which gives rise to "band folding" effects as described in: > > > https://meep.readthedocs.io/en/latest/FAQ/#why-are-there-strange-peaks-in-my-reflectancetransmittance-spectrum-when-modeling-planar-or-periodic-structures > > To obtain the "unfolded" reflectance spectra, the unit cell must contain > just a single disk with the cell dimensions in the periodic dimensions > defined by the lattice constant. > > > _______________________________________________ > meep-discuss mailing list > meep-discuss@ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
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