High accuracy graphene-based refractive index sensor: Analytical approach

Abstract

A high-precision graphene-based refractive index (RI) sensor is suggested in this article. Because resonances represent a specific field distribution, optical sensors show a very high sensitivity to environment RI changes. These optical sensors' sensitivity is profoundly subordinate to the materials used in the sensor as well as the sensor structure. The structure of the proposed sensor consists of the following layers, respectively: gold layer, SiO2, graphene and the substance under test (analyte). The transmission line model (TLM) was also fully investigated for this absorber and the inductor and capacitor values related to the simulation were obtained. There was a suitable agreement between the simulation results and TLM. This sensor has nearly perfect absorption and the absorption peak of this sensor in the absorption curve is 99.99 % at 3.24 THz with an average quality factor of 11.39. This absorber-based sensor sensitivity to changing the test medium (analyte) RI is so high that with a very small change in the RI of the analyte, the absorption peak is shifted, and its frequency changes. This sensor sensitivity and figure of merit (FOM) to variation of the analyte RI 726 GHz/RIU 2.69 RIU-1 were acquired, respectively. The characteristics of this sensor can be adjusted by variating the bias voltage exerted on the graphene layer. The Computer Simulation Technology (CST) and Advanced Design System (ADS) software have been used to analyze this structure. This proposed sensor can be used as a good sensor in biomedical applications and early diagnosis of diseases such as leukemia and types of cancer and influenza.