Graphene-based mid-infrared biosensor

We propose a new graphene-based metamaterial biosensor to achieve tunable plasmon-induced transparency in the mid-infrared (mid-IR) regime. The structure consists of a graphene sheet with three cut-out strips that has been located on a substrate. It is shown that the plasmonically induced transparency (PIT) can be realized by breaking the symmetry of the structure in the normal incidence and also changing the polarization of the incident light in the symmetric case. By optimizing the physical parameters of the antennas, an extremely strong optical sensing coefficient (about 99%) is observed in the mid-IR frequency range based on the PIT effect, which is much larger than that of related previous studies. More importantly, we observed a blueshift in the transparency window through the increase of the gate voltage of the graphene's chemical potential. The transparency window strongly depends on the physical parameters of the substrate and filling material. Furthermore, it is found that the biosensing application of the proposed structure is highly dependent on inserting an ultra-thin buffer layer between the graphene and substrate layer, leading to a tunable PIT in the mid-IR regime. (C) 2017 Optical Society of America