Sensing Performance Analysis of Spiral Metasurface Utilizing Phase Spectra Measurement Technique

We have demonstrated both numerically and experimentally a 2D plasmonic metamaterial the unit cell of which comprised an Archimedean spiral with a C-shaped resonator. Such metasurface enables the excitation of spoof localized plasmon resonances (LPRs) in the terahertz frequency range, similar in properties to the familiar LPRs in the visible range. We have compared the thin-film sensing potentials of the fundamental and dark resonant modes supported by the metasurface in the range of 0.2-0.5 THz. Both the amplitude and phase transmission spectra have been studied. A sensitivity of 21.1%/RIU (78.7 GHz/RIU) and a figure of merit (FOM) of 14.4 RIU-1 have been achieved. The FOM and Q factor obtained from the phase transmission spectra were shown to be about twice higher than those obtained from the amplitude spectra.