Design, Fabrication, and Characterization of Near-IR Gold Bowtie Nanoantenna Arrays

We demonstrate tunable, near-IR plasmonic nanoantennas using a 2D array of relatively large Au bowtie nanoantennas (BNAs) as the design template. We explore the geometric conditions for enhanced plasmonic response for BNAs bound to an SiO2 substrate as well as for BNAs supported on SiO2 pillars. Contrary to previous reports, we perform both systematic experimental and simulation studies exploring the influence of BNA gap spacing, array periodicity, and pillar height on plasmon-resonance-wavelength tunability and maximum field enhancement. We demonstrate that the peak of the plasmon resonance response can be tuned from similar to 1.3 to 2.2 mu m with respect to array periodicity, and a maximum field enhancement of similar to 16000 is theoretically achievable for pillar-supported BNAs (p-BNAs) of height 2.5 mu m and array periodicity of 1.8 mu m-a factor of 4X larger field enhancement than that from substrate-bound BNAs. We also find that the p-BNAs possess a maximum refractive index sensitivity of 1763 nm RIU-1, which is among the highest values reported to date, making the structure attractive for high-sensitivity probing of chemical and biological systems.