Coupled two aluminum nanorod antennas for near-field enhancement
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Aluminum (Al) plasmonic nanoantennas possess many tunabilities in the ultraviolet (UV) region and have a variety of new applications, such as in sensitive UV photodetection and UV photolithography. Using discrete dipole approximation (DDA), the resonant optical properties and enhanced local field distribution of coupled Al nanorod antennas were investigated. The effects of gap distance on the extinction spectra were analyzed to obtain the surface plasmon modes of these nanostructures across the visible and in the UV spectral range, which can be attributed to the coupling of the surface plasmon modes from each Al nanorod. In addition, the enhanced local field factors plotted as a function of gap distance were simulated under transverse and longitudinal polarizations to achieve maximum near-field enhancement for the optical antennas. When the gap distance was decreased to 5 nm, the maximum value of the enhanced factor was 18.04 at the transverse mode peak of 424 nm. This could be explained by the combination of the interaction between the charges distributed at the opposite ends of two Al nanorods and the interaction between the charges distributed at the lateral sides of each Al nanorod. Results showed that the coupled Al nanorod antennas with enhanced local field show promise for UV plasmonics.
Keywordsaluminum (Al) nanorod optical antennas surface plasmon resonance (SPR)
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This work was supported by the National Basic Research Program of China (No. 2013CBA01703), the National Natural Science Foundation of China (Grant No. 21271007), the Foundation for Young Talents in College of Anhui Province (No. 2013SQRL044ZD), the Colleges and Universities Natural Science Foundation of Anhui Province (No. KJ2016JD18).