Using the circular dichroism of a non-chiral metasurface to detect the magnetic fields

Abstract

In this paper, a metasurface composed of an array of V-shaped Ag nanostructures deposited on a magneto-optical material is proposed to control the circular dichroism (CD) effect via an external magnetic field. We numerically observed that this structure due to its nonchirality shows significant CD effect under oblique incidence only. We first considered the case at which the external magnetic field was perpendicular to the metasurface. In this case, the structure indicated a weak sensitivity to the external magnetic field. However, by applying the magnetic field along the plane of metasurface, we observed a strong dependence of CD curve on the external magnetic field. In addition, the CD effect was different for magnetic fields along the x and y directions in the plane of metasurface due to the different symmetries with respect to these axes. The sensitivity of the proposed structure to the external magnetic field was calculated for both cases where the magnetic field was along the plane of metasurface and perpendicular to it. Our results confirmed that this structure was able to sense smaller magnetic fields which were parallel to the metasurface plane compared with ones that were normal to the structure plane.