Sensitive Biosensors Based on Plasmonic-graphene Nanocombinations for Detection of Biological Elements in Blood Samples

In this work, a sensitive biosensor is proposed and investigated based on the combinations of graphene-plasmonic nanostructures. The suggested structure is made of different layers of SiO2, gold (Au), and graphene in the formats of U-shaped, split ring, and straight waveguides. Straight waveguides which are connected to the U-shaped waveguides are denoted as the Input, Output1, Output2, and Output3 ports. The incident light-wave would be applied to the Input port and then would be transmitted to the three output ports with different peak wavelengths (considering the specifications of the structure). In the proposed structure, for improving its functionalities (improving the transmission's peak value and wavelength for biosensing applications), effects of different structural parameters (w(1), t(1), g(1), w(2), t(2), g(2), w(3), t(3), and g(3)) and chemical potentials (mu(c1), mu(c2), and mu(c3)) are considered. After improving the structure's transmission spectrum at different output ports (Output1, Output2, and Output3 ports), vital biological element's concentrations in blood samples (glucose, cholesterol, and creatinine concentrations) would be considered for diagnosis. Finally, considerable sensitivity factors of 1560 nm/RIU "RIU stands for refractive index unit" (for glucose at Output1 port), 2666.6 nm/RIU (for cholesterol at Output2 port), and 1458.3 nm/RIU (for creatinine at Output3 port) are obtained. Also, FWHM and FOM of "13 nm, 120," "19 nm, 76.75," and "15 nm, 177.77" are achieved for glucose, creatinine, and cholesterol, respectively. Therefore, the structure can be considered as an appropriate and efficient candidate for biosensing applications in optical integrated circuits.