Unveiling the bright spot with Mie scattering

Abstract This work applies Mie scattering theory to provide a new perspective on the propagation of light through a spherical obstacle, offering a novel explanation for the formation of the Poisson spot (also known as the Arago or Fresnel spot). We demonstrate that the diffraction patterns generated by a sphere and by a circular disk can be understood as complementary outcomes of the same underlying scattering process. Our analysis highlights the constructive interference responsible for the bright central spot, and extends the classical wave optics framework by connecting it directly with the scattering coefficients of spherical harmonics. This approach not only deepens the theoretical understanding of diffraction phenomena, but also provides a practical framework that may be applied in modern optical experiments and photonic device design.