Abstract
Electromagnetic field absorbers with ultranarrow relative bandwidth () and extremely high peak absorbance () are a challenge in terahertz frequency. In this paper, we propose an insulator-metal-insulator-metal stacked structure with nearly unity peak absorbance () and 0.77% relative bandwidth as an ultranarrowband perfect terahertz absorber. Even though the composite structure contains high reflective metal layers, however, thanks to the introduction of a top insulator, the terahertz field can tunnel through the upper gold film at some functional tunneling bands. As a result, the energy at the Fabry–Perot resonance of the metal-insulator-metal substructure is strongly absorbed due to an enhancement effect. The perfect absorption () and ultranarrowband width properties make the design promising in terahertz devices such as absorbers, filters, narrowband terahertz emitters, etc.
© 2016 Optical Society of America
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