Surface plasmon-enhanced terahertz spectroscopic distinguishing between isomers in powder form

Abstract

The effect of a dielectric overlayer on terahertz transmission through a freestanding metallic array of subwavelength holes is experimentally presented. There is a remarkable resonance redshift from 0.600 to 0.498 THz at the surface plasmon (SP) metal-dielectric resonance mode with increasing film thickness. When the overlayer film is thicker than a critical thickness, the resonance frequency becomes steady at the final resonance frequency ω(f). On the basis of the dispersion relation of SPs, two kinds of glutamic acid enantiomers are distinguished by use of SP-enhanced terahertz spectra of metallic array of subwavelength holes according to the result of ω(f). The terahertz plasmonic hole array with the sensitive nature provides an approach to distinguish trace amount of powder substances, which has a promising application prospect in the fields of public security and biomedical science, such as distinguishing between isomers and identifying expensive medicines and drugs.