Dual-band unidirectional reflectionlessness based on electromagnetically induced transparency-like in three-cavity array

We propose a scheme to realize the dual-band unidirectional reflectionlessness at an exceptional point in a non-Hermitian system based on electromagnetically induced transparency-like effect. This system is constructed with three plasmonic cavities side-coupled to a plasmonic waveguide. Furthermore, our study verifies that the proposed system can consistently realize dual-band unidirectional reflectionlessness in a wide range of phase shifts, coupling strengths, and loss rates. At the same time, the analysis results show that the position of the reflectionless peaks is robust to loss rates, and can be adjusted by tuning the coupling strength between the plasmonic cavities and the plasmonic waveguide, as well as the coupling strength within the double-cavity array.