THz filter based on the Si microdisk array

Compared to plasmonic metasurface, all-dielectric metasurface can suppress radiation loss at terahertz (THz) frequencies due to the low intrinsic loss of dielectric. Here, we propose a THz filter based on all-dielectric metasurface composed of Si microdisk (SiMD) array standing on TPX substrate. Numerical simulation results demonstrate that both electric dipole and magnetic dipole resonances are excited in the SiMD, resulting in a high reflection coefficient of 100%. The working frequency of the designed filter can be passively tuned over a wide range from 1.0 THz to 1.5 THz by manipulating the radius of the SiMD. In addition, the proposed filter is robust to the incident polarizations (x-/y-linear polarizations) and the incident angles (ranging from 0° to 25°). Besides, a new degree of freedom is introduced by cutting a split in the SiMD. The filter can work well even with a split in the SiMD since the presence of the split does not induce additional losses. We further demonstrate the resonant modes can also be modified by tuning the width of the splitting gap, resulting in a tunable THz filter with high efficiency.