Optical bow-tie slot antenna as single polaritonic launcher

Optical antennas, which converts free propagating light into highly confined electromagnetic fields, have been applied to nonlinear optics [1], biochemical sensing [2,3], metamaterials [4], but quite seldom in polaritonics. For instance, nano-infrared-spectroscopy is often used to probe polaritons in 2D crystals, but it offers the difficulty of having multiple polaritonic sources, such as AFM metallic tip, devices metal contacts and the crystal edges. In this work, we propose a bow-tie slot antenna that efficiently launches phonon-polaritons in hexagonal-boron-nitride (hBN). Through finite-difference-time-domain (FDTD) simulations [5], we were able to calculate the antenna's response in the infrared region. The antenna’s geometry was improved by matching its resonance with hBN’s Restrahlen bands, where it exhibits phono-polaritons activity. Simulated polaritonic wavefronts showed circular-like propagation which indicates that polaritons are generated from a single point source.

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[3] van Zanten, T. S., Lopez‐Bosque, M. J., & Garcia‐Parajo, M. F. (2010). Imaging Individual Proteins and Nanodomains on Intact Cell Membranes with a Probe‐Based Optical Antenna. Small, 6(2), 270-275.
[4] Chen, Y., Chen, Y., Chu, J., & Xu, X. (2017). Bridged bowtie aperture antenna for producing an electromagnetic hot spot. Acs Photonics, 4(3), 567-575.
[5] Lumerical, F. D. T. D. (2016). Solutions.

Acknowledgements: This work was supported by the National Council for Scientific and Technological Development (CNPq) and Ministry of Science, Technology, Innovation and Communications (MCTIC).