Abstract
An ultra-multiband terahertz absorber formed by a periodic metallic groove array filled with high-dielectric-constant material is presented. Simulation results show that since multiple Fabry–Pérot cavity modes are excited in the metal groove, the absorber can obtain 15 narrow-band absorption peaks with an average absorptivity over 99.5% at normal incidence. At oblique incidence, all absorption bands still maintain the high absorption above 90% for angles up to 50°. Due to its structural symmetry, the absorber is polarization insensitive. The frequencies and number of the absorption bands can be controlled by turning the depth of the metal groove. In addition, the proposed absorber can be operated as a highly sensitive refractive index sensor. Such an ultra-multiband, polarization-insensitive, and wide-angle absorber structure can be applied in terahertz-related absorption filters, biochemical sensors, or thermal images.
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