Spectral Tuning of Hyperbolic Shear Polaritons in Monoclinic Gallium Oxide via Isotopic Substitution
Abstract
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 ‐Ga 2 O 3 (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 18 O bGO films homoepitaxially grown on a 16 O bGO substrate, we demonstrate a spectral redshift of 40 cm −1 for the 18 O bGO, compared to 16 O bGO. The technique allows for direct observation and a model‐free estimation of the spectral shift driven by isotopic substitution without the need for knowledge of the dielectric tensor. Complementary far‐field measurements and ab initio calculations ‐ in good agreement with the near‐field data ‐ confirm the effectiveness of this estimation. This multifaceted study demonstrates a significant isotopic substitution induced spectral tuning of HShPs into a previously inaccessible frequency range, creating new avenues for technological applications of such highly directional polaritons.
Article Details
Authors (29)
Giulia Carini
Department of Physcial Chemistry Fritz Haber Institute of the Max Planck Society Berlin Germany
Mohit Pradhan
University of Iowa Iowa City USA
Elena Gelžinytė
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Berlin Germany
Andrea Ardenghi
Paul‐Drude‐Institut für Festkörperelektronik Leibniz‐Institut im Forschungsverbund Berlin e.V. Berlin Germany
Saurabh Dixit
Vanderbilt University Nashville TN USA
Maximilian Obst
Interdisciplinary Material Science Vanderbilt University Nashville Tennessee USA
Aditha S. Senarath
Interdisciplinary Material Science Vanderbilt University Nashville Tennessee USA
Niclas S. Mueller
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Berlin Germany
Gonzalo Álvarez‐Pérez
Istituto Italiano di Tecnologia Center for Biomolecular Nanotechnologies Lecce Italy
Katja Diaz‐Granados
Vanderbilt University Nashville TN USA
Ryan A. Kowalski
Vanderbilt University Nashville TN USA
Richarda Niemann
Department of Mechanical Engineering Vanderbilt University Nashville Tennessee USA
Felix G. Kaps
Institute of Applied Physics TUD Dresden University of Technology Dresden Germany
Jakob Wetzel
Institute of Applied Physics TUD Dresden University of Technology Dresden Germany
Raghunandan Balasubramanyam Iyer
University of Iowa Iowa City USA
Piero Mazzolini
Department of Mathematical Physical and Computer Sciences University of Parma Parma Italy
Mathias Schubert
Department of Electrical and Computer Engineering, University of Nebraska-Lincoln 1 , Lincoln, Nebraska 68588,
J. Michael Klopf
Institute of Radiation Physics Helmholtz‐Zentrum Dresden‐Rossendorf Dresden Germany
Johannes T. Margraf
University of Bayreuth, Bavarian Center for Battery Technology (BayBatt), Bayreuth, Germany and Fritz-Haber-Institut der Max-Planck-Gesellschaft 2 , Berlin,
Oliver Bierwagen
Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund 5 , DE-10117 Berlin,
Martin Wolf
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, Berlin 14195, Germany
Karsten Reuter
Theory Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Lukas M. Eng
Susanne C. Kehr
Institute of Applied Physics TUD Dresden University of Technology Dresden Germany
Joshua D. Caldwell
Department of Mechanical Engineering Vanderbilt University Nashville Tennessee USA
Christian Carbogno
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Berlin Germany
Thomas G. Folland
Department of Physics and Astronomy, The University of Iowa 1 , Iowa City, Iowa 52245,
Markus R. Wagner
Paul‐Drude‐Institut für Festkörperelektronik Leibniz‐Institut im Forschungsverbund Berlin e.V. Berlin Germany
Alexander Paarmann
Department of Physcial Chemistry Fritz Haber Institute of the Max Planck Society Berlin Germany