Tunable and Sensitive Refractive Index Sensors by Plasmonic Absorbers with Circular Arrays of Nanorods and Nanotubes for Detecting Cancerous Cells

In this paper, for improving the refractive index sensitivity, we propose different sensor devices by optical metamaterial nanoabsorbers. The presented absorbers are designed by different configurations such as basic model, nanorods, and nanotube array. With three-dimensional finite difference time domain (FDTD) method, their absorption, transmission, and reflection spectra, and sensitivity and figure of merit (FOM) values are numerically investigated. The simulation results show that the resonances at longer wavelengths have higher values of sensitivity and FOM. For presenting the applicability, we examine the sensor for detecting cancerous cells. The proposed absorbers have been coated with an outer material with a thickness of 100 nm and refractive indices of 1 & x2053; 1.2. The maximum sensitivity is obtained at 1055 nm/RIU for the absorber with nanotube array, while its FOM is 19.5 RIU-1. Due to its spectral characteristics, the proposed structures can be used to detect other materials such as human blood group, ethanol, and hemoglobin concentrations of some materials.