Dual-Mode All-Graphene-based Tunable Plasmonic Metasurface for Sensing Applications

In this paper, we have proposed an all-graphene-based multimodal plasmonic metasurface at the mid-infrared region. The unit cell of the metasurface consists of a planar dielectric substrate on which the graphene layer is patterned in circles. Multimodes are achieved by differing the chemical potential of the graphene of the two consecutive patterned circles on the unit cell. The structure has been demonstrated in the transmission mode of operation. From the mid-infrared region to the long wavelength infrared regime, this is tunable by varying the chemical potential of the graphene. Moreover, these multimodes are independent of the angle of incidence. These plasmonic multimodes at this region have different line widths at their resonance point. This is extremely important for sensing applications in this region. We have shown our design to the application for the detection of hazardous methane gas and nitrobenzene. For the demonstration of the sensing, the experimental dispersions have been considered. A maximum sensitivity of 10,128.62 nm/RIU and 12,057.88 nm/RIU have been achieved for methane gas, and 1311.136 nm/RIU and 1949.318 nm/RIU have been achieved for nitrobenzene. The application is not limited to our demonstration. The mid-infrared region is the signature region for most hazardous gases and compounds. With the added advantage of multimodes, our design could also be applied to various spectroscopic applications.