All-silicon periodic and non-periodic THz metasurface for sensing applications

Metasurfaces assisted terahertz time domain spectroscopy have attracted intense attention in sensing field. However, most of the traditional metallic terahertz (THz) metasurfaces are limited in application for their high thermal conductivity, low melting point, complicated design and fabrication. Here, we proposed two different types of all-silicon multi-band THz metasurface with rectangular holes for sensing applications. The periodic multi-band metasurface sensor (PMMS) and the non-periodic multi-band metasurface sensor (NMMS) were designed and fabricated. The absorption characteristics and the resonance mechanism were studied. Both the PMMS and NMMS can achieve more than 90% multi-band resonance absorption. As a demonstration of the sensing applications of PMMS, three different saccharides (fructose, glucose, and sucrose) with the same concentration were investigated experimentally. Furthermore, different concentrations of 2, 4-D solutions were detected by the proposed NMMS, and the sensitivity achieved 2.76✕10⁻² THz/ppm. The proposed all-silicon multi-band THz metasurface sensors with the advantages of low loss, low cost, simple structure and fabrication are expected to provide an alternative approach for sensing applications at the frequency range from radio through THz and to the infrared.