2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/70963We present basic results, known and new, on nontrivial solutions of periodic stationary nonlinear Schrödinger equations. We also sketch an application to nonlinear optics and discuss some open problems.Analysis of PDEsMathematical Physics35Q55; 58E50; 78M30Periodic nonlinear Schrödinger equation with application to photonic crystalstext