Abstract
Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation of graphene SPPs and PWG, the tunable Fano resonances in the terahertz frequency are discussed. It is found that the asymmetric lineshape of Fano resonances can be manipulated by changing the Fermi level of graphene, and the influence of the thickness of coupling layer and air layer in sandwich structure on the Fano resonances is also discussed in detail. We then apply the proposed Fano resonance to realize the ultrasensitive terahertz biosensors, it is shown that the highest sensitivities of 3260 RIU−1 are realized. Our result is two orders of a conventional surface plasmon resonance sensor. Furthermore, we find that when sensing medium is in the vicinity of water in THz, the sensitivity increases with increasing refractive index of the sensing medium.
Highlights
Optical sensors based on surface plasmon polaritons (SPPs) at noble metal surfaces [1,2] have been widely studied since Otto and Kretschmann excited SPPs with attenuated total reflection (ATR) [3,4]
When the wave vector mismatch between an SPP and the incident transverse magnetic (TM) polarized light is compensated, a reflection dip always appears in the reflectance-angle/wavelength spectrum implying the existence of SPP
These sensors are found to be extremely sensitive to the changes in the refractive index of any dielectric attached to the metal surface, which make them have extensive applications in areas such as medical diagnosis [5] environmental monitoring [6] and the analysis of biomolecular interactions [7]
Summary
Optical sensors based on surface plasmon polaritons (SPPs) at noble metal (such as gold and silver) surfaces [1,2] have been widely studied since Otto and Kretschmann excited SPPs with attenuated total reflection (ATR) [3,4]. When the wave vector mismatch between an SPP and the incident transverse magnetic (TM) polarized light is compensated, a reflection dip always appears in the reflectance-angle/wavelength spectrum implying the existence of SPP These sensors are found to be extremely sensitive to the changes in the refractive index of any dielectric attached to the metal surface, which make them have extensive applications in areas such as medical diagnosis [5] environmental monitoring [6] and the analysis of biomolecular interactions [7]. Compared with conventional working spectrum (only from the visible to near-IR wavelengths), but graphene can make up for these plasmonic materials such as noble metals, its THz response can be dynamically tuned by electrostatic problems. Otto geometry for SPP excitation in terahertz frequencies using [13], sensors based on graphene SPPs have been investigated by severalgraphene authors [13,14,15,16,17,18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
