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High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures

Published

Author(s)

Georg Ramer, Mohit Tuteja, Joseph R. Matson, Marcelo I. Davanco, Thomas G. Folland, Andrey Kretinin, Takashi Taniguchi, Kenji Watanabe, Kostya Novoselov, Joshua D. Caldwell, Andrea Centrone

Abstract

The anisotropy of hexagonal boron nitride (hBN) crystals gives rise to hyperbolic phonon polaritons (HPhPs), notable for their volumetric frequency-dependent angular propagation and strong confinement. For frustum (truncated nanocone) structures, theory predicts 5 distinct sets of high-order HPhPs but only one set was observed previously with far-field reflectance and scattering-type scanning near-field optical microscopy (s-SNOM). In contrast, the photothermal induced resonance (PTIR) technique has recently permitted sampling of the full HPhP dispersion and observing such elusive predicted modes; however, the mechanism underlying PTIR sensitivity to these non-radiative modes, while critical to their understanding, has not been yet clarified. Here, by directly comparing conventional contact-mode and newly developed tapping-mode PTIR we show that the PTIR sensitivity to those weakly scattering, high-Q (up to ≈ 280) modes is unrelated to the probe operation (contact or tapping) and is instead linked to PTIR ability to detect tip-launched weakly scattering polaritons, rather than nanostructure- launched HPhPs modes observed by other techniques. Furthermore, we show that in contrast with plasmons and surface phonon polaritons, whose Q-factors and the optical cross-sections are typically degraded by the proximity of other nanostructures, the high-Q HPhP resonances are preserved even in high density hBN frustum arrays, which is useful in sensing and quantum emission applications.
Citation
Nanophotonics
Volume
9
Issue
6

Keywords

PTIR, phonon-polaritons, hBN, s-SNOM

Citation

Ramer, G. , Tuteja, M. , Matson, J. , Davanco, M. , Folland, T. , Kretinin, A. , Taniguchi, T. , Watanabe, K. , Novoselov, K. , Caldwell, J. and Centrone, A. (2020), High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures, Nanophotonics, [online], https://doi.org/10.1515/nanoph-2020-0048 (Accessed August 1, 2021)
Created May 17, 2020, Updated July 8, 2020