Hyperbolic phonon polaritons (HPhPs) are hybrid excitations of light and coherent lattice vibrations that exist in strongly optically anisotropic media, including two-dimensional materials (e.g., MoO). These polaritons propagate through the material's volume with long lifetimes, enabling novel mid-infrared nanophotonic applications by compressing light to sub-diffractional dimensions. Here, the dispersion relations and HPhP lifetimes (up to ≈12 ps) in single-crystalline α-MoO are determined by Fourier analysis of real-space, nanoscale-resolution polariton images obtained with the photothermal induced resonance (PTIR) technique. Measurements of MoO crystals deposited on periodic gratings show longer HPhPs propagation lengths and lifetimes (≈2×), and lower optical compressions, in suspended regions compared with regions in direct contact with the substrate. Additionally, PTIR data reveal MoO subsurface defects, which have a negligible effect on HPhP propagation, as well as polymeric contaminants localized under parts of the MoO crystals, which are derived from sample preparation. This work highlights the ability to engineer substrate-defined nanophotonic structures from layered anisotropic materials.
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http://dx.doi.org/10.1515/nanoph-2020-0640 | DOI Listing |
ACS Appl Opt Mater
December 2024
Department of Physics, Umeå University, Linnaeus väg 24, 901 87 Umeå, Sweden.
Multilayered metal-dielectric nanostructures display both a strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and nonradiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities toward the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control of light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation.
View Article and Find Full Text PDFNanophotonics
March 2024
Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China.
Nat Commun
November 2024
Centre for Nano Science and Technology, Fondazione Istituto Italiano di Tecnologia, Milano, Italy.
Controlling light at subwavelength scales is crucial in nanophotonics. Hyperbolic polaritons, supporting arbitrarily large wavevectors, enable extreme light confinement beyond the diffraction limit. Traditional hyperbolic metamaterials suffer from high losses due to metallic components, while natural low-loss hyperbolic phonon polaritons are limited to the mid-infrared range.
View Article and Find Full Text PDFNat Commun
October 2024
Fritz Haber Institute of the Max Planck Society, Berlin, Germany.
The vast repository of van der Waals (vdW) materials supporting polaritons offers numerous possibilities to tailor electromagnetic waves at the nanoscale. The development of twistoptics-the modulation of the optical properties by twisting stacks of vdW materials-enables directional propagation of phonon polaritons (PhPs) along a single spatial direction, known as canalization. Here we demonstrate a complementary type of directional propagation of polaritons by reporting the visualization of unidirectional ray polaritons (URPs).
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