Fig. 2: Zoom into experimental and calculated spectra at frequencies close to the TO phonon.
From: Microcavity phonon polaritons from the weak to the ultrastrong phonon–photon coupling regime
a Experimental reflectivity spectrum of the MoS2/hBN/MoS2 heterostructure placed on the bottom gold mirror (illustrated by inset), measured before the evaporation of the top gold mirror. Measured thicknesses are 510 nm/10 nm/370 nm. b Experimental reflectivity spectrum of the stack of the panel (a) after closing it with the top Au layer (illustrated by inset). \({\omega }_{-}^{(1)}\) and \({\omega }_{+}^{(1)}\) mark the dips emerging for the coupling between TO phonon and cavity mode. c Simulated reflectivity spectrum of the cavity in panel (b), using layer thicknesses of 510 nm/10 nm/370 nm. d Simulated reflection spectrum of the cavity of the panel (c), in which hBN was replaced by a dielectric medium with \({\varepsilon \left(\omega \right)=\varepsilon }_{{{{{{\rm{hBN}}}}}},{{\infty }}}=\) 4.52. The labels \({\omega }_{{{{{{\rm{cav}}}}}}}^{(1)}\) and \({\omega }_{{{{{{\rm{cav}}}}}}}^{(2)}\) mark the first and second-order cavity mode. e–h Same as panels (a–d) for a MoS2/hBN/MoS2 heterostructure with measured thicknesses 520 nm/100 nm/430 nm and simulated thicknesses 480 nm/100 nm/390 nm. i–l Same as panels (a–d) for a cavity fully filled with hBN, with measured and simulated hBN thickness 1,665 nm. \({\Omega }_{R}={\omega }_{+}^{(1)}-{\omega }_{-}^{(1)}\) in panel l marks the dip splitting. Black and blue curves show experimental and simulation results, respectively, and purple shaded areas highlight the Reststrahlen band.
