I would step back and ask why you want such a small Δt. If you drastically shrink Δt, the accuracy will still be limited by your spatial resolution Δx, so it is not clear what you hope to learn.
Furthermore, if your frequency is 1THz, then a timestep of 0.0264ps is only about 2% of a cycle, so the solution should be changing very slowly on that timescale (in a linear system). If your frequency is < 1THz, e.g. 300GHz, then this is even more true. (Note that the wavelength in vacuum corresponding to 1THz is 0.3mm, so 30pixel/mm would be only 9 pixels per wavelength, which is quite a coarse resolution. But perhaps your actual frequency is more like 300GHz, in which case that spatial resolution is more reasonable — and Δt=0.0264ps is even more unreasonable.) > On Nov 9, 2020, at 12:12 AM, Ardavan Oskooi <ardavan.osk...@gmail.com> wrote: > > Your analysis is correct. Using the default Courant factor of S=0.5 and > resolution of 30 pixels/mm would give Δt = SΔx/c = 55555.56 ps which is six > orders of magnitude larger than what you want. There are only two ways to > reduce Δt: (1) increase the resolution or (2) reduce the Courant factor. > > See also: https://meep.readthedocs.io/en/latest/Introduction/#units-in-meep > <https://meep.readthedocs.io/en/latest/Introduction/#units-in-meep>. > > On 11/7/20 14:21, Gui Max wrote: >> >> I am trying to run the simulation using a THz source. I wish the source to >> have 0.0264ps timestep(deltaT) and a total of about 1000 timesteps. I choose >> the 'a' to be 1mm, as my sample size is about 1 to 2 cm. I calculated my >> deltaT as deltaT = (S/resolution)*(1000/c) , and using resolution = >> 30pixel/mm. However, if I want to achieve my desired deltaT, it would >> require S (Courant Constant) to be a ridiculously small number. Or I can >> keep S=0.5, but the resolution will be extremely large, and I don't need the >> cell sizes to be such fine. What did I do wrong here? Any help would be >> appreciated. >> > _______________________________________________ > 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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