Intercavity phonons and dynamics in coupled polariton cavities

Abstract

Intercavity polaritons, hybrid quasiparticles with spatially separated photonic and excitonic components, provide a platform to engineer structured light-matter states. We show that resonant driving of the middle polariton branch leads to a qualitatively distinct dynamical regime in which coherent Rabi oscillations are suppressed, and the system evolves monotonically toward its steady state. Including interactions, we demonstrate that this regime supports Bogoliubov excitations with a phonon-like dispersion at low momenta. These collective modes inherit interactions from the excitonic fraction, while preserving the intrinsically intercavity nature of the quasiparticles.

Figures (6)

• Figure 1: Schematic representation of two strongly coupled cavities. The left cavity contains only a dielectric medium, while the right cavity hosts an excitonic resonance. The cavities are coupled via a thin metallic mirror that mediates photon tunneling.
• Figure 2: Dynamical formation of intercavity polaritons. Time evolution of the populations $n_L(t)$, $n_R(t)$, and $n_X(t)$ associated with the left cavity photon, right cavity photon, and exciton components, respectively, under resonant pumping of the middle polariton branch. Panels show three representative tunneling-to-coupling ratios: (a) $J/\Omega = 1$, (b) $J/\Omega = 2$, and (c) $J/\Omega = 4$. Dashed horizontal lines indicate the asymptotic steady-state values $Z_L$ and $Z_X$ predicted from the polariton eigenmode composition.
• Figure 3: Transparency window in the steady-state response. Steady-state population of the right cavity $n_R(t=\infty)$ as a function of the exciton detuning $\Delta\omega_X/\Omega$ for different tunneling-to-coupling ratios $J/\Omega$. A characteristic transparency window emerges around zero detuning, reflecting destructive interference between polariton pathways and the formation of a dark state.
• Figure 4: Breakdown of intercavity polaritons due to exciton damping. Steady-state populations $n_i^{\mathrm{ss}}$ of the left cavity ($L$), right cavity ($R$), and exciton ($X$) components as a function of the normalized exciton decay rate $\gamma_X/\Omega$. Increasing $\gamma_X$ progressively suppresses the excitonic population and alters the balance of light–matter hybridization, ultimately destroying the collective polariton state.
• Figure 5: Time evolution of the populations $n_i(t)$ associated with the left-cavity photon (blue), right-cavity photon (orange), and exciton (black) components when the system is coherently driven at the eigenenergy of the (left) lower, (middle) middle, and (right) upper polariton branches. The lower and upper polariton dynamics exhibit pronounced Rabi oscillations before reaching their steady state, reflecting coherent light–matter exchange. In contrast, the middle polariton shows a smooth, non-oscillatory rise toward the steady state, a direct consequence of its purely intercavity character, which suppresses Rabi cycling. We take $J/\Omega=1$ and $\gamma_R/\Omega=0.5$ and $\gamma_L/\Omega=0.1$