We consider the topological aspects of wave propagation in 1D photonic crystals. It was shown by Zak that in 1D structures, bands could be characterized by means of a geometric phase, provided the structure possesses an inversion symmetry, that is the potential V is symmetric with respect to some point. This phase is defined as an integral over the Brillouin zone. We propose another view on the Zak phase, based on a dynamical system approach, that allows to identify the topological properties with the presence of poles of a meromorphic function. This allows to extend the notion to lossy systems. Numerical examples are given in the case of 1D structure whose basic period comprises two slabs filled with a homogeneous material.
|