Terahertz Biochemical Sensor Based on Strong Coupling Between Waveguide Mode and Surface Plasmons of Double-Layer Graphene

Graphene has emerged as a potential plasmonic material for the development of optical devices in terahertz (THz) frequency in the past few years. It is shown that the double-layer graphene can support surface plasmon polaritons (SPPs), which is similar to the long-range SPP of a thin metal layer. By coupling the SPPs of the double-layer graphene with the dielectric planar waveguide (PWG) modes, a THz biochemical sensor is proposed in this paper. Strong coupling between the two modes will occur in the hybrid structure due to the strong resonances, and the sensitivity of the sensor is greatly improved due to the high quality factors of both PWG and double-layer graphene SPPs modes. The proposed sensor has achieved the state-of-art sensitivity of 292 RIU
^-1
, which is nearly doubled compared to the sensitivity of the double-layer graphene SPPs sensor (140 RIU
^-1
) and almost nine times of a conventional graphene SPPs sensor (33 RIU
^-1
). We believe that the proposed biochemical sensor can be used well in THz chemical and biological detection.