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A structure for refractive index sensing application in THz band is proposed and analyzed in this paper. This structure is comprised of a golden plasmonic metamaterial absorber in which water is used as a dielectric and a thin TOPAS layer-which does not have a significant effect on the performance of the sensor- is used for the separation of analyte and water. This structure has an absorption of 99.2% at resonance frequency of 2.8725 THz. Lateral absorption frequency shift occurs due to variation in the refractive index (RI) of the analyte. This structure can be used for refractive index measurement in the range of 1-1.4 with full-width half maximum (FWHM), sensitivity (S), the figure of merit (FoM), and quality factor (Q-factor) in the ranges of 0.01647 THz, 427-644 GHz per refractive index unit (RIU), 6.3-26.5 and 26.23-175.5, respectively. It is worth mentioning that for a limited refractive index range of 1.1 to 1.15, the values of FWHM, Q-factor, and FoM enhance to 0.0053327 THz, 516, and 90, respectively. The simplicity, compactness, and ease of fabrication due to the use of water as a dielectric along with appropriate refractive index sensitivity and FoM help this structure to be used in biological, medical, and environment sensing applications. [ABSTRACT FROM AUTHOR]

A novel metamaterial absorber sensor has been proposed for refractive index measurement in the range of [1-2] for the THz frequency band. This structure is based on using a plasmonic coaxial resonator which is excited by an InSb cylinder. Surface Plasmon Polaritons (SPPs) are excited on the surface of the InSb cylinder due to an inward plane wave and propagate downward toward the cavity and through it. Based on the radius and height of the InSb cylinder, the “high-absorption” and “highquality factor” sensing performance is introduced and analyzed. It is shown that nearly 98% absorption can be achieved for all the range of refractive index [1-2] at 1.8622 THz and in the case of “high-quality factor”, absorption reaches nearly 100% for the refractive index range of [1.5-2]. Also, by changing the radius and height of the cavity, absorption can be changed. Furthermore, sensitivity, quality factor, and figure of merit in the range of 166-672 GHz per refractive index unit (GHz/RIU), 69.1-118.7 and 10.2-29.7 is achievable, respectively. A wide range of refractive index measurements besides superior sensing performance made this structure a good candidate for sensing applications such as medical and biological applications. [ABSTRACT FROM AUTHOR]