Dipole modelling for a robust description of subdiffractional polariton waves

Author(s)

Feres, Flavio H. ^{[1, 2]} ; Barcelos, Ingrid D. ^[1] ; Mayer, Rafael A. ^{[3, 1]} ; dos Santos, Thiago M. ^[1] ; Freitas, Raul O. ^[1] ; Raschke, Markus B. ^{[4, 5]} ; Bahamon, Dario A. ^[6] ; Maia, Francisco C. B. ^[1]

Affiliation

^[1] Brazilian Ctr Res Energy & Mat CNPEM, Brazilian Synchrotron Light Lab LNLS, BR-13083970 Campinas, SP - Brazil

^[2] Sao Paulo State Univ UNESP, Inst Geosci & Exact Sci, Phys Dept, BR-13506900 Rio Claro - Brazil

^[3] Univ Estadual Campinas UNICAMP, Inst Fis Gleb Wataghin, Campinas, SP - Brazil

^[4] Univ Colorado, JILA, Boulder, CO 80309 - USA

^[5] Univ Colorado, Dept Chem, Dept Phys, Boulder, CO 80309 - USA

^[6] Univ Prebiteriana Mackenzie, MackGraphe Graphene & Nanomat Res Ctr, BR-01302907 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: NANOSCALE; v. 11, n. 44, p. 21218-21226, NOV 28 2019.
• Web of Science Citations: 0

Abstract

The nanophotonics of van der Waals (vdW) materials relies critically on the electromagnetic properties of polaritons defined on sub-diffraction length scales. Here, we use a full electromagnetic Hertzian dipole antenna (HDA) model to describe the hyperbolic phonon polaritons (HP(2)s) in vdW crystals of hexagonal boron nitride (hBN) on a gold surface. The HP2 waves are investigated by broadband synchrotron infrared nanospectroscopy (SINS) which covers the type I and type II hyperbolic bands simultaneously. Basically, polariton waves, observed by SINS, are assigned to the resultant electric field from the summation over the irradiated electric fields of dipoles distributed along the crystal edge and at the tip location and a non-propagating field. The values of polariton momenta and damping extracted from the HDA model present excellent agreement with theoretical predictions. Our analysis shows that the confinement factor of type I HP(2)s exceeds that of the type II ones by up to a factor of 3. We extract anti-parallel group velocities (v(g)) for type I (v(g,typeI) = -0.005c, c is the light velocity in a vacuum) in relation to type II (v(g,typeII) = 0.05c) polaritonic pulses, with lifetimes of similar to 0.6 ps and similar to 0.3 ps, respectively. Furthermore, by incorporating consolidated optical-near field theory into the HDA model, we simulate real-space images of polaritonic standing waves for hBN crystals of different shapes. This approach reproduces the experiments with a minimal computational cost. Thus, it is demonstrated that the HDA modelling self-consistently explains the measured complex-valued polariton near-field, while being a general approach applicable to other polariton types, like plasmon- and exciton-polaritons, active in the wide range of vdW materials. (AU)

• FAPESP's process: 18/05425-3 - Cavity effect of the Phonon-Polaritons in Graphene-Hexagonal boron nitride two-dimensional heterostructure
• Grantee: Flávio Henrique Feres
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 15/11779-4 - Plasmonic and nonlinear effects in graphene coupled to optical waveguides
• Grantee: Christiano José Santiago de Matos
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/08818-9 - Modulation of polaritons amplitude by two-dimensional dielectric junctions in the light of synchrotron infrared nanospectroscopy
• Grantee: Rafael Alves Mayer
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 18/07276-5 - Mid- and far-infrared plasmonic biosensing with graphene
• Grantee: Christiano José Santiago de Matos
• Support Opportunities: Regular Research Grants