As an addendum to my earlier post, here is a link to some C++ source code I'm trying to use. Even though the computation prints out results for a number of frequencies, I'm looking specifically at the result for 1.81 which should correspond to 45 degrees and 550nm light with the k-value I have chosen. I expect 11% but get around 31%.
http://pastebin.com/m6731fd4a ~Adam Isom On Fri, Jun 19, 2009 at 10:30 AM, Adam Isom <[email protected]> wrote: > 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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