Realization of broadband terahertz reflector by all-dielectric monolayer grating

We exploit Mie resonances in all-dielectric grating metamaterials to design a single-negative all-dielectric near-perfect reflector. The average reflection over 99.9% at single frequency in terahertz region is achieved. Ultrabroadband perfect reflector was proposed by all dielectric single-layer super cell grating metamaterial structure. It consists of two Silicon grating strips with different width in single unit cell, which possesses peak reflection over 99.9% and a near-perfect reflection band of 0.79THz from 1.19THz to 1.98THz, surpassing the reflectance of metallic mirrors. The coupling effect of Si grating elements with different width is revealed by magnetic and electric dipole Mie resonances. The physic mechanism of broadband perfect reflection is disclosed by the electromagnetic field distribution of super cell grating. Polarization effect of perfect reflection is also studied. The proposed super cell metamaterial structure can be potentially applied to other photonic devices to realize broadband effect.