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Strong Coupling of Exciton-Polaritons in a Bulk GaN Planar Waveguide: Quantifying the Coupling Strength

Abstract : We investigate the demonstration and quantification of the strong coupling between excitons and guided photons in a GaN slab waveguide. The dispersions of waveguide polaritons are measured from T = 6 to 300 K through gratings. They are carefully analyzed within four models based on different assumptions, in order to assess the strong-coupling regime. We prove that the guided photons and excitons are strongly coupled at all investigated temperatures, with a small (11%) dependence on the temperature. However, the values of the Rabi splitting strongly vary among the four models: the "coupled oscillator" model overestimates the coupling; the analytical "Elliott-Tanguy" model precisely describes the dielectric susceptibility of GaN near the excitonic transition, leading to a Rabi splitting equal to 82 ± 10 meV for fundamental transverse-electric mode; the experimental ellipsometry-based model leads to smaller values of 55 ± 6 meV. We evidence that, for waveguides including active layers with large oscillator strengths, as required for room-temperature polaritonic devices, a strong bending of the modes' dispersion is not necessarily the signature of the strong coupling, which requires for its reliable assessment a precise analysis of the material dielectric susceptibility.
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Submitted on : Tuesday, December 1, 2020 - 4:12:19 PM
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C. Brimont, L. Doyennette, G. Kreyder, F Réveret, P. Disseix, et al.. Strong Coupling of Exciton-Polaritons in a Bulk GaN Planar Waveguide: Quantifying the Coupling Strength. Physical Review Applied, American Physical Society, 2020, 14 (5), ⟨10.1103/physrevapplied.14.054060⟩. ⟨hal-03034132⟩



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