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A high-sensitivity sensing technique was demonstrated based on a flexible terahertz dual-band metamaterial absorber. The absorber has two perfect absorption peaks, one with a fundamental resonance (f1) of the structure and another with a high-order resonance (f2) originating from the interactions of adjacent unit cells. The quality factor (Q) and figure of merit of f2 are 6 and 14 times larger than that of f1, respectively. For the solid analyte, the changes in resonance frequency are monitored upon variation of analyte thickness and index; a linear relation between the amplitude absorption with the analyte thickness is achieved for f2. The sensitivity (S) is 31.2% refractive index units (RIU-1) for f2 and 13.7% RIU-1 for f1. For the aqueous solutions, the amplitude of absorption decreases linearly with increasing the dielectric constant for the ethanol-water mixture of f-1. These results show that the designed absorber cannot only identify a solid analyte but also characterize aqueous solutions through the frequency shift and amplitude absorption. Therefore, the proposed absorber is promising for future applications in high-sensitivity monitoring biomolecular, chemical, ecological water systems, and aqueous biosystems. [ABSTRACT FROM AUTHOR]

An ultrabroad and sharp transition bandpass flexible terahertz (THz) filter is designed using a multiple-layered metamaterial. This bandpass filter has excellent filtering capability, with a 3 dB bandwidth of about 0.47 THz and sharp band-edge transitions of 80 dB/THz and 96 dB/THz, respectively, and it can be realized by a coupling individual resonance mode. We find that the geometry parameters have an influence on the transmission profile, which are capable of giving us meaningful guidance in design of high profile bandpass THz filters. The numerical results show that the multiple-layered flexible metamaterial provides an effective way to achieve ultrabroad THz devices. [ABSTRACT FROM AUTHOR]