Enhanced Optical Transmission through a Hybrid Bull's Eye Structure Integrated with a Silicon Hemisphere.

In this work, we demonstrate a novel structure that can generate extraordinary optical transmission with a silicon hemisphere placed on a conventional bull's eye structure. There is a single subwavelength aperture surrounded by concentric periodic grooves on a substrate. The extraordinary optical transmission in this work is realized by the coupling of the surface plasmon polaritons in the periodic grooves and the localized electromagnetic field generated by the Mie resonance in the silicon hemisphere. The maximum normalized-to-area transmission peak can reach up to 662 with a decreasing device area and size. The electromagnetic field distribution at different geometry parameters is analyzed to clarify the mechanisms of the work in this paper. Additionally, the use of dielectric material in the aperture can avoid ohmic losses of metal material compared with the conventional one, which may suggest that a wider range of bull's-eye-structure applications is possible.

Independently tunable all-dielectric synthetic multi-spectral metamaterials based on Mie resonance.

A single metamaterial (MM) is generally designed to operate in only one band, and the MMs with different dimensions of meta-atoms are required to be integrated to achieve multi-spectral responses simultaneously. In this study, an all-dielectric synthetic multi-spectral metamaterial (SMM) that can efficiently operate in the visible and terahertz (THz) ranges by incorporating nanoscale features into microscale unit cells is demonstrated and investigated numerically. The resonant frequency of the proposed SMM in both regimes can be tuned independently by changing the geometric parameters such as diameter, gap, width and height of unit cells functional in two different regions, whilst maintaining high reflectance efficiency. Results show that a variety of colors can be produced from red to purple in the visible range with maximal reflectance as high as 83% while the peak frequency of the SMM can be adjusted from 8.12 to 2.13 THz in the THz range with maximum reflectance up to 94%. The reflection characteristics of the SMM mainly originate from the electric dipole (ED) and magnetic dipole (MD) resonances via Mie scattering in both regions. The strategy of this research offers the possibility of applications in bio/chemical sensing, multi-spectral imaging, filtering, detection, modulation and so on.