We presented and manufactured a triple-band terahertz (THz) metamaterial absorber with three concentric square ring metallic resonators, a polyethylene terephthalate (PET) layer, and a metallic substrate. The simulation results demonstrate that the absorptivity of 99.5%, 86.4%, and 98.4% can be achieved at resonant frequency of 0.337, 0.496, and 0.718 THz, respectively. The experimental results show three distinct absorption peaks at 0.366, 0.512, and 0.751 THz, which is mostly agreement with the simulation. We analyzed the absorption mechanism from the distribution of electric and magnetic fields. The sensitivity of the three peaks of this triple-band absorber to the surrounding is 72, 103.5, 139.5 GHz/RIU, respectively. In addition, the absorber is polarization insensitive because of the symmetric configuration. The absorber can simultaneously exhibit high absorption effect at incident angles up to 60° for transverse electric (TE) polarization and 70° for transverse magnetic (TM) polarization. This presented terahertz metamaterial absorber with a triple-band absorption and easy fabrication can find important applications in biological sensing, THz imaging, filter and optical communication.

Organophosphate insecticides with broad spectrum and high efficiency make a great difference to agricultural production. The correct utilization and residue of pesticides have always been important issues of concern, and residual pesticides can accumulate and pass through the environment and food cycle, resulting in safety and health hazards to humans and animals. In particular, current detection methods are often characterized by complex operations or low sensitivity. Fortunately, using monolayer graphene as the sensing interface, the designed graphene-based metamaterial biosensor working in the 0–1 THz frequency range can achieve highly sensitive detection characterized by spectral amplitude changes. Meanwhile, the proposed biosensor has the advantages of easy operation, low cost, and quick detection. Taking phosalone as an example, its molecules can move the Fermi level of graphene with π–π stacking, and the lowest concentration of detection in this experiment is 0.01 μg/mL. This metamaterial biosensor has great potential in detecting trace pesticides, and its application in food hygiene and medicine can provide better detection services.