Emergence of multiple phase bands and exceptional points branches in periodic PT-Symmetric coupled waveguides

We propose and study a new, to the best of our knowledge, periodic PT-Symmetric optical scheme consisting of two waveguides with alternating gain/loss sections. The structure exhibits multiple EPs and PT-Symmetric/Broken-symmetry regions, even for negligible gain/loss. The positions of these branches can be changed not only by the level of gain/loss but also by modifying the periodicity of the structure, thus allowing controllable dynamics and on-demand switching between symmetry phases.