  In the present work, we demonstrate that structured light beams are
constituted by two traveling waves which transverse components are in opposite
directions, that is, incoming and outgoing from the axis of propagation. These
waves result from the complex sum of the two fundamental solutions of the
transverse component of the spatial wave equation. After a partial obstruction
of the beam, the incoming and outgoing waves can be easily observed during the
self-healing process, providing a simple explanation of the phenomenon.
Incoming and outgoing waves in Laguerre-Gauss beams are investigated
analytically, numerically and experimentally. The proposed way to describe
light beams might offer new insights into the phenomenon of diffraction.
