## Multi Slit Interference

Posted 11th September 2021 by Holger

This week I have been playing around with my electromagnetic wave simulation code MPulse. The code simulates Maxwell’s equations using an algorithm known as finite-difference time-domain, FDTD for short. Here, I am simulating the wave interference pattern behind the screen with n slits. For $n=1$ there is only one slit and no interference at all. The slit is less than the wavelength wide so you can see the wave spreading out at a large angle. When $n>1$ the slits are 5 wavelengths apart. With $n=2$ you have the classical double-slit experiment. At the right side of the simulation box, the well-known interference pattern can be observed. For 3 slits the pattern close to the slits becomes more complicated. It settles down to a stable pattern much further to the right. For numbers 4, 5 and 6 the patterns become more and more interesting. You would expect the development of sharper lines but it turns out that, for these larger numbers, the simulation box just wasn’t big enough to see the final far-field pattern.

MPulse is open-source and is available at https://github.com/holgerschmitz/MPulse.

The code uses MPI parallelization and was run on 24 cores for this simulation.

MPulse is a work in progress and any help from enthusiastic developers is greatly appreciated.

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