In this paper we propose an approach based on the Dynamical Diffraction Theory (DDT) is presented in order to derive an analytic formulation of superprism effect that exhibit an extremely high angular dispersion. We apply the theory to a one dimensional Photonic Crystal (1D-PhC) at the wavelength of 1.55μm. We demonstrate that it is possible to obtain an angular dispersion of 9.73°/nm by using a structure of Si/SiGe, which represent among the higher dispersion available in literature.