Structured light routing in CROW-endowed add-drop filters

In this paper, we study propagation of optical vortices (OVs) through the add-drop filter that comprises coupled resonators optical waveguide (CROW). We develop a fully-vectorial theory not based on transfer matrix formalism and apply it to the description of CROWs based on multimode fibers. We study transmission of higher-order OVs through CROW-endowed add-drop filter and demonstrate the possibility to transmit such OVs along the CROW chain. We show that during such transmission OVs may invert their topological charges and determine the condition, under which an OV propagate without such charge inversion. We suggest that such system can be used for generation of OV frequency combs. We also study group delay time and show that this system may be used as time delay line for OVs.