Reconfigurable plasmonic hot spots enabled by composite VO2-gold plasmonic antennas

Abstract

We theoretically investigate the formation of electric and magnetic hot spots with reconfigurable plasmonic antennas. We consider three material systems offering different levels of reconfigurability: gold with the static response, vanadium dioxide which allows for ON/OFF switching, and composite gold-vanadium dioxide material platform which offers a possibility to switch between the electric and magnetic hot spot within a single antenna. Using bowtie and diabolo antennas as a case study, we evaluate optical response functions (scattering and absorption cross-sections, electric and magnetic field enhancement). We demonstrate that the composite material system brings, in addition to enhanced reconfigurability, also novel features of plasmonic antennas, such as strong optical absorption and a joint electric-magnetic hotspot.

Figures (4)

• Figure 1: (a) Bowtie and diabolo antennas with schemes of their operation and formation of hot spots. (b) Bowtie (left) and diabolo (right) antennas involved in our study: gold (first row), vanadium dioxide (second and third row), and composite (fourth row). The color of individual PA parts indicates their material composition: gold (yellow), metallic VO$_2$ (red), and insulating VO$_2$ (blue).
• Figure 2: Optical cross sections of bowtie and diabolo PAs. (a,b) Absorption cross section (a) and scattering cross section (b) of the bowtie PAs: gold bowtie PA (yellow line), metallic VO$_2$ bowtie PA (red line), insulating VO$_2$ bowtie structure (blue line), and composite VOwtie PA (green line). (c,d) Absorption cross section (c) and scattering cross section (d) of the diabolo PAs: gold diabolo PA (yellow line), metallic VO$_2$ diabolo PA (red line), insulating VO$_2$ diabolo structure (blue line), and composite diaVOlo PA (green line).
• Figure 3: Normalized electromagnetic field produced by the VOwtie and diaVOlo PAs: planar cross sections at the height of 10 nm above the upper surface of PAs. PA boundaries are indicated by the white line. (a,b) The electric (a) and the magnetic (b) field of the VOwtie PA. (c,d) The electric (c) and the magnetic (d) field of the diaVOlo PA.
• Figure 4: Normalized electromagnetic field produced by the bowtie and diabolo PAs: Spectral dependence at the point above the center of the PA, 10 nm above the upper surface. (a,b) The electric (a) and the magnetic (b) field of the bowtie PAs. (c,d) The electric (c) and the magnetic (d) field of the diabolo PAs. The colors indicate the material composition: gold (yellow), metallic VO$_2$ (red), and composite (green).