Self-referenced integrated plasmonic device based on engineered periodic nanostructures for sensing application

Abstract

A plasmonic device with a self-referenced capability that uses periodic nanostructures has been proposed and analyzed in terms of the spectral response. Aluminum-based periodic nanostructures that scatter incoming radiation towards a thin homogeneous metal layer, are used to excite Surface Plasmons (SP) for normal incident light. The rigorous coupled wave analysis method is used to engineer the periodic nanostructures and evaluation of performance parameters. The sensitivity, figure of merit and reflective amplitude are considered as the main parameters for engineering the device. The electromagnetic field simulations reveal the presence of waveguide mode and two plasmonic modes, namely, SP mode and substrate mode with three different interactions in the device. The shift in SP mode is used to detect the minute changes in the refractive index of the analyte and the number of exciting waveguide modes is used to capture the changes in the thickness of the analyte. The presence of substrate mode adds the self-reference capability to the proposed plasmonic device due to the independence of any change in the refractive index and thickness of the analyte. The proposed device has been engineered to offer a competitive sensitivity of 1000 nm/RIU and figure of merit 300 RIU-1 with the fabrication constraints taken into account. Since the proposed structures work under normal incidence conditions which makes this design integrable to the end of an optical fiber that can be used both to excite SP and to interrogate the spectral reflectance.