Bowtie nanoantennas with void defects

The surface plasmon resonance (SPR) modes and near field gap enhancement of bowtie nanoantennas with void defects are studied numerically. According to the location of the defects, we classify them into four categories: inner, edge, base and vertex defects. Inner and base defects have little impact on SPR modes and gap enhancement while edge and vertex defects lead to mode splitting and gap enhancement changing because of the symmetry breaking. When defects on the edge getting closer to the gap, the gap enhancement increases even above that of the bowtie with no defects. These properties are useful for the evaluation of bowtie nanoantennas fabrication. Furthermore, we can extend the control of the defect location to the defect properties to get useful resonant modes and increase the gap enhancement in applications such as broadband light harvesting, ultrafast wavelength-sensitive photodetection and fluorescent detection for two or more targets.