Optimized Sensitivity and Electric Field Enhancement by Controlling Localized Surface Plasmon Resonances for Bowtie Nanoring Nanoantenna Arrays

The surface plasmon resonances of gold bowtie nanoring antenna arrays were simulated using the finite-difference time-domain method in the present study. Both the local field and transmission spectra of bowtie nanoring antennas with various nanohole sizes were examined to find the optimum conditions to induce the greatest local electromagnetic field enhancement and sensitivity compared to the solid bowtie antenna. With the optimized nanohole size of bowtie nanoring, the local electromagnetic field enhancement, the decay length of the electric field, and the bulk sensitivity were increased as high as about 73, 349, and 63 %, respectively, compared to the solid bowtie antenna. The electric field enhancement profile and the charge distribution of the bowtie nanoring antennas were studied to characterize the coupled plasmon configurations, and it was used to explore the mechanism of enhanced sensitivity and resonance-wavelength shift of bowtie nanoring array with different surrounding dielectric media. This highly localized electromagnetic field enhancement and sensitive bowtie nanoring array system can be applied in the field of surface-enhanced Raman scattering and bio-sensing.