Graphene Nanoribbon Assisted Refractometer Based Biosensor for Mid-Infrared Label-Free Analysis

In this paper, an enhanced Fabry-Perot resonator (FPR)-based refractometer sensor is proposed using graphene nanoribbon (GNR) material to enable mid-infrared application. The FPR section consists of a three vertically aligned GNR sections: a conventional basic section placed in the middle complemented with two ending tail arms for auxiliary enhancement. To enable a real-world application of sensor, three-dimensional (3D) finite difference time domain (FDTD) simulations are performed. To apply dynamic gate bias tuning, the GNR layer is isolated from the substrate by means of a 50-nm layer of silicon dioxide (SiO2), which is placed on top of a thick bulk silicon (Si). To realize sensing application for the proposed enhanced FPR, a container is placed on FPR. Refractive index sensitivity of the sensor is calculated to be in the range of 3180-4220 nm RIU-1. To compare the superior performance of the sensor, a figure of merit (FOM) is defined and extensively investigated. The FOM of proposed sensor is found to be around 2.9-3.1 RIU-1, which is a reasonable value compared to compact-sized on-chip-intended sensors. Moreover, methods of dynamic variation of resonance wavelength are discussed, which can be useful for multi-analytic applications using spectral multiplexing of the sensor. The small footprint and its single- or multi-sensing application suggest that this enhanced FPR-assisted biosensor can be used as a lab-on-a-chip sensor for a label-free analysis.