Dear Prof.Johnson and others: Thanks.
If I only want the period in Y direction: (set-param! k-point (vector3 0 0 0)) ; firstly set the X,Y,Z directions into periodic boundary, because I saw many people do this in this mail list (set! pml-layers (list (make pml (direction X)(thickness dpml)) (make pml (direction Z)(thickness dpml)) )) ; secondly change the X,Z directions into PML When I do this, MEEP trace an error: "infinite period for "set-param! k-point"" 2008/8/11 Steven G. Johnson <[EMAIL PROTECTED]> > On Aug 9, 2008, at 3:02 PM, Ryan Hao wrote: > > 1. about the duplication command in MEEP > > How to infinite duplicated the computational cell in one > > direction in MEEP? > > > If I understand your question correctly, the right way to "infinitely" > duplicate the computational cell in one direction in Meep is to use > periodic boundary conditions. > > (There is a way to set the boundaries to be periodic in only one > direction, if that is what you are asking. But you almost never need > this capability in my experience: if you have PML layers in the other > "non-periodic" directions, it doesn't matter what their boundary > conditions are. Remember that PML is a layer of "material" adjacent to > the boundary, and is totally independent of the boundary condition.) > > > T= S1/S1' (S1 and S1' has the same detector. S1 is hole > > structure, S2 is without hole structure) > > But in my opinion, the transmission spectrum should define as: > > T= S1/S2 (S1 and S2 have different detector. Si is detector > > at output, S2 is detector at input) > > No, you don't want S2 to be the power from a detector at the input. > There are two problems with this: > > First, you *must* do a second "control" simulation without the > scatterer(s). Otherwise, even if you put a flux plane at the input, it > will include the input power minus the reflected power. > > Second, with a typical source, you will couple not only to the > waveguide mode (or whatever your input channel is), but you will also > couple into modes you don't want (e.g. radiating modes). Because of > this, you want to put your normalization flux S2 in your "control" > simulation far enough away from your source that the radiating/leaky > modes will have decayed away. > > You can see how this worked in the example: the control is the > waveguide without any holes, because in that case we want the > transmission relative to the power the source couples into the uniform > waveguide. But the, just like the field example shown in the > tutorial, the source will couple power into radiating modes as well as > into the waveguide mode, so your detector needs to be far enough away > from the source. (For the same reason, your scattering structure > needs to be far enough away from the source that the coupling from > radiating modes doesn't play a significant role. If you are > wondering how far is "far enough," the way to check is the same way > one checks all other convergence issues in numerical methods: double > the distance from your source to the scatterer/detector, and make sure > the answer doesn't change to within your desired error tolerance.) > > Now, it is true that your control simulation can probably get away > with a smaller computational cell than your simulation with the > scatterers. However, usually it's more convenient just to use the > same computational cell in both cases. > > Steven > > _______________________________________________ > meep-discuss mailing list > [email protected] > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss > -- ============================== Sincerely Yours, Ryan Hao PhD candidate Wuhan National Laboratory for Optoelectronics College of Optoelectronic Science and Engineering, Huazhong University of Science & Technology, Wuhan, 430074, P.R.CHINA Phone: 86-027-87792242-809(O) Website: http://www.wnlo.net/spm/People_Ryan_Hao.html http://wnlo.hust.edu.cn/spm/People_Group.html
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