In this paper, we construct a $\mathcal{PT}$-symmetric periodic structure with one-dimensional two-material waveguide networks and primarily investigate reflectionlessness. The formation conditions for reflectionlessness is presented in terms of the incident wave frequency and the number of unit cells. We show that, for this optical system, the orientation of unidirectional reflectionlessness can be controlled by tuning the spacing between waveguides with loss and gain. We also show the energy distribution when reflectionless light propagates through this $\mathcal{PT}$-symmetric optical structure. Finally, we find that unidirectional invisibility of the $\mathcal{PT}$-symmetric periodic structure could be achieved easily by adjusting the number of unit cells. Our results could be potentially important for developing a new generation of functional optical devices with singular directional responses.

• Received 23 May 2019

DOI:https://doi.org/10.1103/PhysRevA.100.033832