Theory, simulation, fabrication, and characterization of Galois scattering plates for the optical and the THz spectral range

Scattering and scattering plates have a large diversity of applications. Scattering of optical and THz electromagnetic waves can be performed with Galois scattering plates, which had found applications in acoustics first (i.e., with sound waves in concert hall acoustics). For binary Galois scattering plates, the single scattering entities, i.e., mesas (for a binary 1) or voids (for a binary 0), have characteristic lateral dimensions of half the wavelength of the electromagnetic waves to be scattered. Their optimal height is a quarter of the wavelength for plates used in reflection. Meanwhile, not too elaborate lithographic techniques allow for the implementation of Galois plates for the THz range and even for the visible spectral range. We had reported on such scattering plates before. However, in this paper, also the mathematical concept is described and the fabrication technologies are emphasized. In contrast to the case of scattering plates with irregular surface morphologies, Galois plate scattering is not diffuse, but there are many scattering/diffraction orders.