Hello everyone, I am trying to compute reflection coefficients for a very simple scenario using Meep: plane wave source and a single, free thin film. My original setup used a 2D grid with PML along all boundaries and a plane source across the top of the grid, with the film at the bottom (I set eps to be the IOR squared). I used the flux computation method from the tutorial with my flux line about halfway between the source and film. The source is a Gaussian centered between 1/700nm and 1/400nm. The results I get for this are very close to the analytical results I already have, but uniformly shifted by a small amount. Anyway, I'm more or less happy with this part.
Now I am trying to capture the reflectance coefficients for multiple angles of incidence. I would like to create a 2D dataset with reflectance percentage as a function of incident light angle and wavelength. Using the flux method in the tutorial, I can get all of the wavelengths I need from a single run. However, I am having trouble with handling multiple angles. I've read some posts concerning this on the mailing list, and it seems that I can get multiple angles using a spatial FT and running my simulation once for each angle I need. I am not a physicist, but I assume that since the spatial FT is decomposing my source into multiple plane waves traveling in different directions, the source should be modeled as a point source instead of a plane source. I have done this, using a similar setup as before. This time the source is a point source and I have PML only on the top and bottom boundaries, with a Bloch periodic boundary condition in the X direction. Using the formula theta = arcsin(kx/w) I have run some simulations using k-values which I believe should give me the correct reflection coefficient for a single angle and frequency according to the formula. Instead what I get is pretty off in terms of both magnitude and the general shape of the plot in terms of wavelength. Eventually I would like to be able to simulate interference effects for somewhat arbitrary materials, and be able to capture reflectance coefficients that are functions of wavelength, incident light angle, and far-field viewing angle. I have a feeling that my understanding of how to do this in Meep has some major flaws, but if this sounds right then I can include my C++ Meep code if it would help. Thanks for your help, ~Adam Isom
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