Abstract
Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO2) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO2 as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide. By combining accelerator-based IR-THz sources (synchrotron and free-electron laser) with s-SNOM, we employed nanoscale far-infrared hyper-spectral-imaging to uncover a Fabry–Perot cavity mechanism in SnO2 nanobelts via direct detection of phonon-polariton standing waves. Our experimental findings are accurately supported by notable convergence between theory and numerical simulations. Thus, the SnO2 is confirmed as a natural hyperbolic material with unique photonic properties essential for future applications involving subdiffractional light traffic and detection in the far-infrared range.
Highlights
Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes
They exist from THz to mid-IR spectral frequencies, within Reststrahlen bands (RBs), situated between tfrreaqnusveenrcsiaels2,3ð.ωITnOÞnanaonsdtrulcotnugreitdudpionlaalr ðωLOÞ optical phonon dielectric materials, Phonon polaritons (PhPs) enable confinement of light beyond the diffraction limit[3,4] allowing super-resolution imaging[5], thermal emission[6], data storage[7] and offer several advantages, mainly related to the usual higher quality factors and significant lower optical losses[8] of PhPs compared to plasmon polaritons[9]
Our findings expand the possibilities of SnO2-NBs from an established 1D-semiconductor to a unique multimode hyperbolic material naturally optimized for the realization of subdiffractional resonators and, potentially, waveguiding in the far-IR range
Summary
Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. We employed SINS to experimentally access the full spatialspectral response and imaging of PhPs in SnO2-NBs. Free-space broadband mid- to far-IR synchrotron radiation is strongly confined at the apex of a metallic AFM tip
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