Accidental bound state in the continuum in a chain of dielectric disks

Dielectric resonators are open systems whose eigenmodes couple to the radiation continuum resulting in nonzero radiation losses. For a long time, it was believed that only guided modes with frequencies below the light line were decoupled from the radiation continuum [1] . In the early 2000’s, several counterexamples of perfectly localized states – i.e. totally decoupled from the radiation continuum – at frequencies above the light line were proposed in dielectric gratings and photonic crystal waveguides [2] . Such states are known as bound states in the continuum (BIC) .