13. Silicon Nanowires for DNA Sensing

Highly sensitive hybrid plasmonic slot waveguide (HPSW) biosensors based on silicon on insulator (SOI) are proposed and analyzed for DNA hybridization detection. The reported designs are based on increasing the light interaction with the sensing region by using slot waveguide with plasmonic material. Due to the high index contrast and plasmonic effect, an ultrahigh optical confinement is achieved in the low-index regions which enables the detection of the smallest change in the analyte refractive index with high sensitivity. The normalized power confinement, power density, effective index of the supported modes by the HPSWs are analyzed to achieve high power confinement through the suggested biosensors, and hence, high sensitivity can be obtained. The HPSWs are also incorporated with straight slotted resonator to calculate the sensitivity of the proposed design. In this study, two different plasmonic materials (gold and titanium nitride) are used for the proposed designs. The simulation results are calculated using full vectorial finite element method (FVFEM). The reported biosensors have high sensitivity of 1890.4 nm/RIU (refractive index unit) with a detection limit of 2.65 × 10⁻⁶ RIU with gold material and 1190 nm/RIU with a detection limit of 4.2 × 10⁻⁶ RIU based on titanium nitride material, which are the highest in the literature to the best of our knowledge.