Abstract
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 ${\varepsilon _{\text{re}}}$, ${\mu _{\text{re}}}$, and ${\boldsymbol \Gamma}$, whereas the interior medium is quantified by ${\varepsilon _{\text{ri}}}$, ${\mu _{\text{ri}}}$, and $\beta$. 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, ${\boldsymbol \Gamma}$, and $\beta$. Zero backscattering is possible if, in addition to impedance-matching condition, the object is rotationally symmetric about the propagation direction, and ${\boldsymbol \Gamma}$ is parallel to the propagation direction. Numerical results confirm these remarks for scattering by spheroids. On fixing ${\varepsilon _{\text{ri}}}$, ${\mu _{\text{ri}}}$, ${\varepsilon _{\text{re}}}$, and ${\mu _{\text{re}}}$, the effects of ${\boldsymbol \Gamma}$ and $\beta$ 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 ${\boldsymbol \Gamma}$ and $\beta$. The total scattering efficiency when ${\boldsymbol \Gamma}$ is coparallel to the propagation direction can be either equal to, larger than, or smaller than when ${\boldsymbol \Gamma}$ is antiparallel or perpendicular to the propagation direction, depending on $\beta$ and the electrical size of the sphere. It is found that parallel propagation of the incident plane wave with respect to ${\boldsymbol \Gamma}$ has a stronger influence than perpendicular propagation, regardless of $\beta$ and the electrical size of the sphere. The effect of increasing/decreasing the magnitude of ${\boldsymbol \Gamma}$ can be envisioned only when its direction is parallel to the propagation direction.
© 2021 Optical Society of America
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