Polariton Condensation in Photonic Molecules

We report on polariton condensation in photonic molecules formed by two coupled micropillars. We show that the condensation process is strongly affected by the interaction with the cloud of uncondensed excitons and thus strongly depends on the exact localization of these excitons within the molecule. Under symmetric excitation conditions, condensation is triggered on both binding and antibinding polariton states of the molecule. On the opposite, when the excitonic cloud is injected in one of the two pillars, condensation on a metastable state is observed and a total transfer of the condensate into one of the micropillars can be achieved. Our results highlight the crucial role played by relaxation kinetics in the condensation process.

Figure 1

(a) Emission spectrum measured on a single molecule at low excitation power ($d=4\mu \mathrm{m}$ and $d_{\mathrm{CC}}=3.73\mu \mathrm{m}$); $A$ and $B$ indicate the binding and antibinding states, respectively. Inset: Scanning electron micrograph of an array of pillars and molecules. (b) Emission spectra measured on a $4\mu \mathrm{m}$ round micropillar (black line) and on photonic molecules with $d=4\mu \mathrm{m}$ and various values of $d_{\mathrm{CC}}$. (c) Left (right) column: Measured (calculated) emission pattern of the four lowest energy modes of a photonic molecule with $d=4\mu \mathrm{m}$ and $d_{\mathrm{CC}}=3.73\mu \mathrm{m}$. (d) Schematic of the hybridization of the individual pillar modes within a photonic molecule.

Figure 2

Excitation at the center of the molecule: (a)–(c) spectrally resolved emission distribution along the molecule axis measured for several excitation powers; (d)–(f) calculated emission patterns for several excitation powers. $d=4\mu \mathrm{m}$ and $d_{\mathrm{CC}}=3.46\mu \mathrm{m}$. $\delta =-3\mathrm{meV}$.

Figure 3

Excitation at the center of the molecule: (a) integrated intensity measured as a function of the excitation power; (b) splitting between the two lowest energy emission lines measured as a function of the excitation power; (c) lowest energy emission lines measured with a polarization parallel (solid line) and perpendicular (squares) to the molecule axis for $P=0.05P_{\mathrm{th}}$; (d) the same as (c) for $P=7P_{\mathrm{th}}$. The inset shows the calculated spatial shape of the binding state.

Figure 4

Asymmetric excitation: (a)–(c) spectrally resolved emission distribution along the molecule axis measured for several excitation powers; (d)–(f) calculated emission patterns for several excitation powers. $d=3.5\mu \mathrm{m}$ and $d_{\mathrm{CC}}=3.1\mu \mathrm{m}$. $\delta =-3\mathrm{meV}$.