Nanoscale-confined Terahertz Polaritons in a van der Waals Crystal

Abstract

Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light-matter interactions, thus enabling light manipulation in deep sub-wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures - such as antennas or nanoslits - with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons - light coupled to lattice vibrations - in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses. However, experimental demonstration of nanoscale-confined phonon polaritons at THz frequencies has so far remained elusive. Here, we provide it by employing scattering-type scanning near-field optical microscopy (s-SNOM) combined with a free-electron laser (FEL) to reveal a range of low-loss polaritonic excitations at frequencies from 8 to 12 THz in the vdW semiconductor $\alpha -Mo{O}_3$. We visualize THz polaritons with i) in-plane hyperbolic dispersion, ii) extreme nanoscale field confinement (below ${\lambda }_o/75$) and iii) long polariton lifetimes, with a lower limit of > 2 ps.

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Cited by in corpus (17)

• Hybridized hyperbolic surface phonon polaritons at α-MoO3 and polar dielectric interfaces
• Nanoscale-confined Terahertz Polaritons in a van der Waals Crystal
• Enabling propagation of anisotropic polaritons along forbidden directions via a topological transition
• In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes
• Germanium monosulfide as a natural platform for highly anisotropic THz polaritons
• Unidirectional Ray Polaritons in Twisted Asymmetric Stacks
• Near-Field Terahertz Nanoscopy of Coplanar Microwave Resonators
• Terahertz nanospectroscopy of plasmon polaritons for the evaluation of doping in quantum devices
• Hyperbolic phonon polaritons and wave vector direction dependent dielectric tensors in anisotropic crystals
• Low-loss far-infrared surface phonon polaritons in suspended SrTiO3 nanomembranes
• Observation of Coherent Ferron Emission and Propagation
• Misalignment between the Directions of Propagation and Decay of Nanoscale-confined Polaritons
• Plasmons in two-dimensional electron systems with infinite and semi-infinite metal gratings
• Real-space nanoimaging of THz polaritons in the topological insulator Bi2Se3
• Retrieving optical parameters of emerging van der Waals flakes
• Two-dimensional talc as a natural hyperbolic material
• Long-range mid-infrared energy transfer mediated by hyperbolic phonon polaritons