On the optical field confinement at the anapole mode in nanohole silicon metasurfaces

Abstract

Recently, researchers demonstrated numerous types of the metasurfaces with non-radiating states including the anapole ones. These metasurfaces have promising properties for various applications in optics which are mainly connected with the optical field confinement. But by itself, the existence of the anapole state does not make one available to exploit this feature. For example, Ospanova et al. [\textit{Laser \& Photonics Rev.}, 2018, vol. 12, p. 1800005] presented a grouped nanohole array in silicon slab possessing anapole mode in visible range. In this work, it is proved that despite of the existence of the anapole mode in the proposed nanostructure the valuable electric field confinement is not reached. Thus most expected uses of the anapole state cannot be gained through this nanostructure. As demonstrated here, the aforementioned nanostructure may be replaced by the square nanohole array having the anapole state with different meta-atom and much larger electric field confinement.