Tuning the optical response of a plasmonic T-shaped dimer with nanowire loads for improved SERS and sensing applications

Plasmonic nanostructures have important applications for surface-enhanced Raman chips, optical sensors, perfect absorbers, and so on. In this paper, we theoretically investigate the optical properties of a T-shaped dimer (TD) nanostructure and a TD with nanowire loads (TD/NL) nanostructure. By depositing the NLs around the TD, the optical property of the TD is significantly modified, and the extinction spectrum of composite TD/NL appears the splitting resonance peak and shows the asymmetric characteristic of Fano resonance due to the plasmon hybridization. Besides, a stronger electric field enhancement can be obtained in the composite TD/NL nanostructure, and the calculated results show the field enhancement effect of the dark mode in designed TD/NL nanostructure is three times than that in the TD nanostructure. Furthermore, the Fano resonance in TD/NL nanostructure reveals the narrow spectral linewidth and high quality factor, which is advantageous to optical refractive index sensors, and the corresponding sensing sensitivity is as high as 1083 nm RIU−1.