Design of Extremely Sensitive Refractive Index Sensors in Infrared for Blood Glucose Detection
Sandeep Kumar Chamoli, Subhash C. Singh, Chunlei Guo
Abstract
Simple and easy to fabricate sensors with high sensitivity, high quality-factor (χ), large figure of merit (FOM), and narrow bandwidth are highly desirable for immediate point of care testing. In this article, we introduce a onedimensional periodic array of barium flint glass on active plasmonic material, a thin gold film on silicon nitride (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) substrate. Reflection spectrum of the proposed structure exhibits a clear rejection of certain wavelength on normal incidence due to the coupling between incident plane wave and plasmonic wave. The effect of ambient refractive index or glucose concentration has been studied to measure the plasmonic sensitivity of the designed structure in blood glucose detection. After optimizing geometric parameters, the designed sensor achieved sensitivity and quality factor as high as ~ 2600 nm RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (refractive index unit) and ~1500 respectively. The calculated sensitivity, quality factor and FOM are much higher than the reported structures with a similar geometry in IR. Owing only one rejection band with narrow bandwidth, the designed structure can also be realized for optical filtering applications. Wide spectral tunability in the IR, close to 100 % peak absorbance and narrow bandwidth make the designed structures as an ideal candidate for surface-enhanced infrared absorption (SEIRA) spectroscopy.