Metal Oxide Grating Based Plasmonic Refractive Index Sensor With Si Layer in Optical Communication Band

Abstract

Nanostructure based devices are crucial for many applications including surface plasmon resonance (SPR) sensors, in particular. In this work, an aluminum oxide (Al2O3) grating based plasmonic sensor with Si and Ag layers is proposed and simulated for the detection of hemoglobin (Hb) concentration (en route its refractive index measurement) in human blood in optical communication band (1400-1550 nm). The simulations are based on rigorous coupled wave analysis (RCWA). In general, a plasmonic sensor's performance is closely evaluated in terms of sensitivity and figure of merit (FOM) but we have also extended the analysis by considering the SPR curves (of both reference and analyte samples) even more meticulously in terms of spectral FOM (FOM*) based on depth of reflectance curve. In order to further deepen the performance analysis, a quality factor (QF) is introduced by combining the maximum FOM* (m-FOM*) and FWHM of the analyte SPR curve. The effect of grating variables and the thicknesses of Si and Ag layers on FOM* and QF is analyzed. The simulation results are explained in relevant physical concepts such as radiation damping. The results indicate that the proposed sensor with optimized design parameters is able to provide significantly better sensitivity, detection limit, FOM, and m-FOM* compared with existing grating-based SPR sensors.