Possible Photon Trajectories in a System of Two Twisted Optical Slits

We compare four different ways of calculating the possible paths for photons in a twisted slit system with elementary Huygens light waves. The first way leads to a surface of the stationary phase and its geodesics in the Fresnel function approximation, and describes the classical channel of photon trajectories [1a-d]; the second way is similar but uses a graphical method instead of an integration, the third way is based only on momentum conservation at the slits [1e], and these three are opposed to the results of a numerical integration. Summing up we find momentum conservation [1e] to be the dominant effect in describing possible photon trajectories in a system of narrow slits in free space.