2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/86656A time-domain approach is proposed for the propagation of ultrashort electro- magnetic wave packets beyond the paraxial and the slowly-varying-envelope approximations. An analytical method based on perturbation theory is used to solve the wave equation in free space without resorting to Fourier trans- forms. An exact solution is obtained in terms of successive temporal and spatial derivatives of a monochromatic paraxial beam. The special case of a radially polarized transverse magnetic wave packet is discussed.3 pages, General vectorial derivationOpticstext