Plane wave scattering by a three-dimensional chiral object immersed in a simple Lorentz-nonreciprocal medium with magnetoelectric gyrotropy

Scattering by a three-dimensional object composed of a chiral medium (the interior medium) and immersed in a simple Lorentz-nonreciprocal medium with magnetoelectric gyrotropy (the exterior medium) was treated using the extended boundary condition method (EBCM). The exterior medium is quantified by ε_re, µ_re, and 0, whereas the interior medium is quantified by ε_ri, µri, and β. When irradiated by a plane wave, the differential scattering efficiency does not depend on the polarization state of the incident plane wave if the exterior medium is impedance-matched with the interior medium, regardless of the shape of the object, 0, and β. Zero backscattering is possible if, in addition to impedance-matching condition, the object is rotationally symmetric about the propagation direction, and 0 is parallel to the propagation direction. Numerical results confirm these remarks for scattering by spheroids. On fixing ε_ri, µri, ε_re, and µ_re, the effects of 0 and β on the total scattering efficiency were examined for a sphere. The total scattering efficiency does not depend on the polarization state of the incident plane wave, even when the exterior medium is not impedance-matched with the interior medium, and despite the presence of 0 and β. The total scattering efficiency when 0 is coparallel to the propagation direction can be either equal to, larger than, or smaller than when 0 is antiparallel or perpendicular to the propagation direction, depending on β and the electrical size of the sphere. It is found that parallel propagation of the incident plane wave with respect to 0 has a stronger influence than perpendicular propagation, regardless of β and the electrical size of the sphere. The effect of increasing/decreasing the magnitude of 0 can be envisioned only when its direction is parallel to the propagation direction.