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arXiv · 2606.11239

Direct observation of anisotropic surface phonon polaritons on \alpha-quartz

Ryoga Odawara·Kotaro Shirahata·Aozora Ohi·Shun Hashiyada·Yukio Kawano
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Abstract

Anisotropic surface phonon polaritons (SPhPs) offer extremely strong light confinement and unique light propagation characteristics, particularly on anisotropic polar crystals. Despite the classical importance of \alpha -quartz as a prototypical uniaxial bulk crystal, real-space observation of anisotropic SPhP propagation on \alpha-quartz has remained elusive. In this study, we report the first direct observation of SPhP propagating on an \alpha-quartz surface using scattering-type near-field optical microscopy (s-SNOM). We demonstrate that the dispersion relation and propagation length of SPhPs exhibit remarkable anisotropy depending on the propagation direction relative to the optic axis of \alpha-quartz. Furthermore, we verify that these experimental behaviors agree with theoretical calculations based on the dielectric permittivity tensors. Our results establish \alpha-quartz as a robust, highly promising platform for light-controlling nanodevices and mid-infrared on-chip sensing.

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Ryoga Odawara, Kotaro Shirahata, Aozora Ohi, Shun Hashiyada, Yukio Kawano. 2026-05-29. Direct observation of anisotropic surface phonon polaritons on \alpha-quartz. https://arxiv.org/abs/2606.11239

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