Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas

Abstract

Launching and manipulation of polaritons in van der Waals materials offers novel opportunities for field-enhanced molecular spectroscopy and photodetection, among other applications. Particularly, the highly confined hyperbolic phonon polaritons (HPhPs) in h-BN slabs attract growing interest for their capability of guiding light at the nanoscale. An efficient coupling between free space photons and HPhPs is, however, hampered by their large momentum mismatch. Here, we show —by far-field infrared spectroscopy, infrared nanoimaging and numerical simulations— that resonant metallic antennas can efficiently launch HPhPs in thin h-BN slabs. Despite the strong hybridization of HPhPs in the h-BN slab and Fabry-Pérot plasmonic resonances in the metal antenna, the efficiency of launching propagating HPhPs in h-BN by resonant antennas exceeds significantly that of the non-resonant ones. Our results provide fundamental insights into the launching of HPhPs in thin polar slabs by resonant plasmonic antennas, which will be crucial for phonon-polariton based nanophotonic devices. ; The authors acknowledge financial support from the European Commission under the Graphene Flagship (GrapheneCore2), the Spanish Ministry of Science, Innovation and Universities (national projects MAT2017-88358-C3, MAT2015-65159-R, MAT2015-65525-R, RTI2018-094830-B-100, RTI2018-094861-B-100, and the project MDM-2016-0618 of the Marie de Maeztu Units of Excellence Program) the Marie Sklodowska-Curie individual fellowship (SGPCM-705960), the Basque Government (PhD fellowship PRE 2018 2 0253), and the project PIC201660E046 from CSIC. M.M.W. acknowledges support from the Konrad-Adenauer-Stiftung. P.A.G. acknowledges support from the European Research Council under Starting Grant 715496, 2DNANOPTICA. ; Peer reviewed