Array of photonic hooks generated by multi-dielectric structure

Abstract

Generation of array of photonic hooks (PHs) by a multi–dielectric structure that consists of periodically arrayed scatterer units has been systematically studied. The study focuses on the effects of geometric and optical parameters of the multi–dielectric structure on the characteristics of generated PHs, especially their bending angles. These geometric and optical parameters include size, shape, refractive index and number of scatterer units, and their adjacent spacing. The results show that the spacing, size and refractive index play a predominant role in tailoring the performance of the PHs array, and the spacing affects mainly the characteristics of a pair of symmetrical PHs while the size and refractive index differences between scatterer units affect mainly those of asymmetrical PHs as a result of the introduction of optical inhomogeneity. In the aspect of scatterer shape, for a multi–dielectric structure that consists of some cylinders, as the light wave is incident parallel (perpendicular) to the cylinder axis, its scattering characteristics are similar to those of the multi–dielectric structure that consists of some cuboids (spheres). In particular, for a structure consisted of cylinders or cuboids with long length in the z direction, an intensive photonic nanojet is additionally generated and located between the paired PHs provided that the wave is incident perpendicular to the cylinder axis or the longest side of cuboid. In the aspect of scatterer unit number, the multi–dielectric structures of odd and even scatterer units generate PHs with different characteristics. The paired PHs generated by multi–dielectric structure with equal spacings always bend outward. However, the paired PHs may bend inward provided that the multi–dielectric structure is designed properly. We have also studied the features of 2D PHs array. The results show that the 2D PHs array displays similar features to the 1D case. The application potential of both 1D and 2D PHs arrays is evaluated.