Study and Simulation of MIM Grating-Based Refractive Index Sensor for the Detection of Haemoglobin (Hb) in Blood Samples

Surface plasmon resonance (SPR)–based biosensors have been an emerging area in recent years in the field of nanotechnology for biomolecule detection. Such sensors can be a replacement for traditional bulky sensors that are available in industries. Our study aims to design a less complex structure that can detect haemoglobin (Hb) concentration in blood. Hb is an essential protein in human blood that carries oxygen in red blood cells. The concentration of haemoglobin in human blood can determine if a person (male and female) is unwell or having any metabolic issues. We simulated the structure through the Lumerical FDTD (finite-difference-time-domain) method. Our design is a three-layer biosensor that has a top grating layer made of a dielectric which is placed on a plasmonic metal gold (Au) and deposited on a SiO₂ substrate. We calculated different performance parameters such as sensitivity, full width half maxima (FWHM), quality factor (QF), and detection accuracy (DA). Additionally, we investigated the plasmonic response over the infrared range and got sharp peaks in the wavelength range between 1350 to 1550 nm and sensitivity that ranges from 664 to 781 nm/RIU for the refractive index (RI) range 1.30–1.47, which can be considered optimal. The findings of our study pave the way to fabricate a simple refractive index-based sensor for the detection of biomolecules in the visible to near-infrared region.