11 / 2019-03-11 15:16:50

All-dielectric broadband terahertz metamaterial absorber and its sensing detection of chlorpyrifos pesticide

all-dielectric broadband absorber, terahertz spectroscopy, semiconductor metamaterial, signal enhancement, pesticide detection

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have shown novel properties and revealed the feasibility of using them as signal enhancement tool to trace minor changes of samples. In this regard, we propose an all-dielectric broadband terahertz absorber in highly-doped silicon-based sensing chips. This semiconductor metamaterial absorber exhibits an experimental absorption (interaction efficiency) of ∼ 99 % at 1.33 THz and a broad bandwidth (absorption of ≥ 90%) that covers 600 GHz of the center frequency. The measuring results are well agreed with the simulations and calculations, and the wide tunability of the absorber is verified by optical excitation. Furthermore, we demonstrate that this metamaterial, which operates at THz frequencies as a highly sensitive THz sensor, has shown promising potential in the detection of trace pesticides. The detection of chlorpyrifos reaches 0.1 mg∙L^(-1). The regression coefficients obtained based on the spectra intensity and frequency shifts are 0.9943 and 0.9750, respectively. These results indicate that the combination of THz spectroscopy and metamaterials can be used in detection of chemical and biological materials with high sensitivity, providing a new strategy for future applications in the fields of food and agriculture.