Manipulating near-field enhancement using hybrid bowtie nanoantenna for SERS

Abstract The metallic bowtie antenna has shown great potential to enhance surface-enhanced Raman scattering (SERS) and various nonlinear optical effects by leveraging near-field amplification produced through localized surface plasmon resonance (LSPR). However, traditional BNA antennas rely heavily on narrow nanogaps to excite strong dipole⎯dipole interactions, which induce field enhancement effects and cause significant light scattering issues. According to theoretical analysis and numerical simulations, this study proposes a method to improve near-field enhancement in hybrid bowtie nanoantennas by exciting dark plasmon modes. Specifically, this dark plasmon mode is achieved by coupling large metal-insulator-metal (MIM) structures with small arrays of silver (Ag) nanorods in the nanogap. This quasi-dark plasmon mode not only significantly reduces scattering loss but also supports stronger near-field enhancement. MIM-BNA nanostructures with arrays of Ag nanorods exhibit a local electric field amplitude approximately eight times greater than that of a pure Ag-BNA nanoantenna with the same nanogap width. This demonstrates the great potential of the improved BNA nanoantenna for SERS applications.