Asymmetric Cross-Shaped Optical Antennas with Wide Spectral Tunability and High Optical Cross-Sections

Resonant optical antennas (ROAs) are nanodevices that can enhance the electromagnetic field in their vicinity and scatter the light in the far field. The enhanced field is localized in subdiffraction-limited volume. Their ability to exhibit strong field enhancement in the gap makes them suitable for coupling with quantum emitters. This paper introduced two novel bimodal and triple-modal asymmetric cross-shaped optical nanoantenna designs. The performance of the reported nanoantennas is numerically studied via the finite element method (FEM). The electric field enhancements and optical cross-sections are calculated to characterize the performance of the designs. These nanoantennas are low-symmetry and polarization-sensitive devices. Furthermore, the reported plasmonic nanostructures exhibit two or three tunable resonances in the optical and near-infrared wavelength regions with ultra-high field enhancement. The reported coupled cross-shaped exhibits a field enhancement of 45.9 for the high-energy resonance and 149.4 for the low-energy resonance, respectively, on |E$_{TOT}$|/|E$_{IN}$| scale.