Journey from the center of the Poincaré sphere

We present a simple and accessible experiment to introduce the Stokes formalism and the Poincaré sphere as powerful tools for describing the polarization state of light. Within this framework, we analyze one of the earliest polarizers: a system consisting of a stack of tilted dielectric plates oriented near Brewster's angle, which acts as a progressive polarizer as the number of plates increases. We derive analytical expressions for the transmission of unpolarized light and the resulting increase in the degree of polarization using the Stokes formalism, incorporating both Fresnel coefficients and internal reflections within each plate. Finally, we validate the theoretical predictions through experiments by tracking the evolution of the polarization state via the Stokes parameters and discussing its trajectory on the Poincaré sphere.