Using Mirror-Based Terahertz Metamaterial Sensor to Chiral Identification and Detection of D-/L- Serine

The particularity of terahertz wave makes it widely used in material detection. The sensitivity to surface medium of metamaterials promotes the development of chiral recognition technology, which is of great significance to the research of life science, medicine and nutrition. In this paper, a pair of ‘S’ mirror structures (‘R-S’ and ‘L-S’) are designed by using finite-different time-domain (FDTD) method and fabricated in micro-machining process. The sensing effect of mirror structures is studied in experiments for chiral recognition and concentration detection of D-serine and L-serine, using the terahertz time-domain transmission system (THz-TDS). Experimental results show that the sensing sensitivity of ‘R-S’ structure to L-serine (3408 GHz/mg·μL
^-1
) is greater than that of D-serine (2356 GHz/mg·μL
^-1
), but the sensing sensitivity of ‘L-S’ structure to L-serine (1162 GHz/mg·μL
^-1
) is lower than that of D-serine (2164 GHz/mg·μL
^-1
), and the minimum detection limit of mirror structures for serine solution is 0.0001 mg/μL. Based on the characteristics of the surface current and the variation of refractive index of samples, the sensing mechanism of mirror structures is deeply studied. It indicates that ‘S’ mirror structures can recognize the chirality of serine and detect the concentration of its aqueous solution. Due to the simple experimental process, easy operation and nondestructive, this method provides an important reference value for the identification of chiral substances.