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

Abstract

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 6.65 THz RIU−1 with a figure of merit (FOM) of 1187 RIU−1 for Fermi level energy ranges from 0.4 to 1.2 eV, making the sensor potential for ultra‐sensitive SPR sensing in the terahertz regime.

Wideband tunable perfect absorption of graphene plasmons via attenuated total reflection in Otto prism configuration

“…Finally, we would like to point out that our proposed Otto prism configuration is essentially different from the configuration where graphene plasmons are excited by a prism, as discussed in Refs. [51][52][53][54]. For the latter configuration, a high-refractive-index prism is used to provide a sufficient wave vector to excite plasmons in a continuous graphene sheet, and thus the resonant wavelength is sensitively dependent on the incident angle.…”

Near-infrared tunable surface plasmon resonance sensors based on graphene plasmons via electrostatic gating control

“… 37 In terahertz spectrum, it was found that the momentum mismatch between the highly confined plasmon modes in homogeneous graphene sheets and the incident radiation could be alleviated by increasing the surface conductivity of graphene through high doping levels or with few layer graphene, and by adopting high-index coupling prism. 38 Several prism configuration GSPR sensors with doped graphene for angular interrogation sensing, 39 frequency interrogation sensing, 40 and phase interrogation sensing 41 in THz spectrum were studied theoretically.…”

Excitation of localized graphene plasmons by a metallic slit

“…Since the dispersion properties of SPPs are extremely sensitive to the dielectric constant of the surrounding medium, plasmonics structures are widely used for molecular and biosensing [40]. The use of graphene in plasmonic biosensors [41,42] has an additional advantage, since the above-mentioned tunability of the plasmonic resonance frequency allows for achive it in the spectral range where the strength of the characteristic molecular signal is the highest [43].…”