A directional nanoantenna design based on a hybrid plasmonic waveguide: theoretical analysis for biosensing applications.

This paper presents a novel rectangular aperture nano-antenna (RANA) design based on a hybrid plasmonic waveguide (HPW) configuration. The performance of the HPW is evaluated through theoretical analysis and compared with results from the Finite Integration Technique (FIT). The overall performance of the RANA is investigated at an operational frequency of 450 THz using both FIT and the Finite Element Method (FEM). The nano-antenna exhibits a directional radiation pattern, which is leveraged for refractive index biosensing. The biosensor's performance is characterized using a dry protein model with a refractive index ranging from 1.7 to 1.9. The sensing mechanism relies on monitoring shifts in the beam direction and variations in the power flow peak in response to changes in the refractive index of the dry protein as a material under test (MUT). The proposed biosensor achieves a sensitivity of 34.5 degrees per refractive index unit (RIU). The biosensor maintains strong performance over a 2 percent bandwidth centered at operational frequency, enhancing its detection robustness.