2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/196935Light propagation is investigated in the context of local anisotropic nonlinear dielectric media at rest with the dielectric coefficients $ε^μ_ν= ε^μ_ν(\vec{E},\vec{B})$ and constant $μ$, in the limit of geometrical optics. Birefringence was examined and the general conditions for its occurrence were presented. A toy model is exhibited, in which uniaxial birefringent media with nonlinear dielectric properties could be driven by external fields in such way that birefringence may be artificially controlled. The effective geometry interpretation is also addressed.5 pages, 1 figureGeneral Relativity and Quantum Cosmologytext