Surface plasmon enhanced terahertz spectroscopic distinguishing between isotopes

We present an experimental demonstration of surface plasmon enhanced terahertz spectroscopic identification of methyl alcohol isotopes by use of metallic array of subwavelength holes. Due to isotopic hydrogen/deuterium substitution, the refractive indices of methyl alcohol and isotopes vary from each other in the terahertz regime. This leads to a modification in the wave vector and consequently the resonance condition of surface plasmons excited at the metal–dielectric interface. A distinct resonance shift and an amplitude modification are observed, giving high characterization sensitivity and thereby demonstrating that such plasmonic array has potential in developing new techniques in isotope distinguishing.