Hi Mario,
Sometimes impossible transmission coefficients arise from placing the flux lines too close to the scatterer. Try to make sure your flux lines are separated from the scatterer by a distance of a wavelength, and not right next to the scatterer as you describe. Also, make sure the flux lines are a wavelength away from sources or pml. You will probably need to increase the size of your air layers to do this. If this gets you good results, you can try to decrease the distances to the flux planes to speed up the simulation. Some other things you can check are to make sure your PML layers are thick enough, and also that you run the simulation long enough (to a small enough decay). If you had a loss-free system, you would be able to tell that your results are correct by observing the losses. Since you don't have this, you have to do several convergence analyses to see whether the losses converge when you increase the resolution, play with the source settings, increase the pml thickness, etc. Best, Matt On Tue, 3 Jun 2008, Mario Cao wrote: > Hello, > > I send one question the 8th April and I have not got any reply. > I would be very pleasured if somebody could help me one jsut give me > some leads to go on. > > Thank you very much once again, > Mario Cao > > --- > > At first, I want to thank you all the help you are offering in the > meep-discuss mailing-list. > > My problem is that I have the following structure with different dielectric > materials with dispersion and > I want to calculate the absorption (the loss) only in the Germanium(Ge) > layer, but I am not sure how. > > Source is placed in the first Air-layer(1) and the simulation is run in 2D > (propagation direction is x) > > * ____________________________________ > *|* | | | | | > *|* | | | | | > *|* Air | Si | Ge | Si | Air | > *|* | | | | | > *|*______|______|______|______|______| > * 1 2 3 4 5 > > I tried to calculate the loss coefficient with the help of flux areas > (lines) just before the Ge-layer and just after the Ge-layer. > But the results are not the expected, because the transmission coefficient > is greater than 1. (not logical) > > I do not know how to deploy this measure, because in the example of the > tutorial "Transmission spectrum around a waveguide bend" > there is one first simulation without dielectric and another one with > dielectric. > In my case with many dielectric-layers, it is possible to calculate the loss > with the flux areas? How should be the first simulation? > And if not, how could I calculate the absorption or loss of this layers? > > Thank you in advance. > > Best regards, > Mario Cao > > PS: Sorry if my english is not very clear. > _______________________________________________ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
