Tunable ultrasensitive terahertz sensing based on surface plasmon polariton of doped monolayer graphene

We reported the surface plasmon resonance (SPR) on doped monolayer graphene (MLG) for terahertz (THz) sensing of refractive index of testing samples using a prism-coupling attenuated total reflection configuration. The theoretical detection range and sensitivity of the THz plasmonic sensor were investigated. The sensor performance in terms of variation of detection accuracy with different refractive index was explored. It was demonstrated that the Fermi level energy of MLG and also the gap distance between the prism base and the MLG had great effects on the performance of THz sensing. The gap distance not only caused the coupling resonance frequency shift in the reflection spectrum, but also affected the full width at half maxima (FWHM) of the SPR curve. The incident angle of THz radiation was also the key impact factor of the detection accuracy of the sensor. The effective SPR frequency could be tuned by controlling the incident angle or the Fermi level energy. The results revealed the maximum sensitivity of the THz plasmonic sensor up to 6.65THzRIU(-1) with a figure of merit (FOM) of 1187RIU(-1) for Fermi level energy ranges from 0.4 to 1.2eV, making the sensor potential for ultra-sensitive SPR sensing in the terahertz regime.