Spectral Tuning of Hyperbolic Shear Polaritons in Monoclinic Gallium Oxide via Isotopic Substitution.

ABSTRACT: Hyperbolic phonon polaritons - hybridized modes arising from the ultrastrong coupling of infrared light to strongly anisotropic lattice vibrations in uniaxial or biaxial polar crystals - enable to confine light to the nanoscale with low losses and high directionality. In even lower symmetry materials, such as monoclinic β$\beta$ -Ga₂O₃ (bGO), hyperbolic shear polaritons (HShPs) further enhance the directionality. Yet, HShPs are intrinsically supported only within narrow frequency ranges defined by the phonon frequencies of the host material. Here, we report spectral tuning of HShPs in bGO by isotopic substitution. Employing near-field optical microscopy to image HShPs in ¹⁸O bGO films homoepitaxially grown on a ¹⁶O bGO substrate, we demonstrate a

SUBMITTER: Carini G 

PROVIDER: S-EPMC12921354 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature