Scattering phenomenon ofPT-symmetric dielectric-nanosphere structure

Abstract

The scattering properties of the $\mathcal{PT}$-symmetric dielectric dual nanosphere structure are investigated through scattering matrix formalism. We calculate the extinction, scattering, and absorption cross sections of the $\mathcal{PT}$-symmetric scatterer illuminated by the monochromatic linearly polarized plane wave with different incident direction. When the size parameter of distance between the dielectric spheres' centers is small, the $\mathcal{PT}$ scatterer is in the unbroken phase due to strong interaction between the active and dissipated spheres. The extinction cross section of the $\mathcal{PT}$ scatterer is always the same when the plane wave is incident from opposite directions with the same polarization. It implies that the light transmission is reciprocal whether the $\mathcal{PT}$ scatterer is in the broken or unbroken phase, because the $\mathcal{PT}$ scatterer is a linear optical scattering system for which the Lorentz reciprocity holds. However, the scattering cross section is different when the plane wave is incident from the loss and gain regions, respectively, and the scattering asymmetry is large when the interaction between active and dissipated spheres is strong. In addition, we find that the absorption cross section of the scattering structure is always negative in the broken phase due to the dominated light scattering of the active sphere.