Room-Temperature Polariton Parametric Scattering Driven by a One-Dimensional Polariton Condensate

We demonstrate a novel way to realize room-temperature polariton parametric scattering in a one-dimensional ZnO microcavity. The polariton parametric scattering is driven by a polariton condensate, with a balanced polariton pair generated at the adjacent polariton mode. This parametric scattering is experimentally investigated by the angle-resolved photoluminescence spectroscopy technique under different pump powers and it is well described by the rate equation of interacting bosons. The direct relation between the intensity of the scattered polariton signal and that of the polariton reservoir is acquired under nonresonant excitation, exhibiting the explicit nonlinear characteristic of this room-temperature polariton parametric process.

Figure 1

(a) Scanning electron microscope image of a single ZnO microwire. $\mathbf{c}$: the crystallographic axis. (b) The angle-resolved photoluminescence spectral ($\mathit{k}$-space) mapping under cw excitation. Both TE (electric field component of light $\overrightarrow{\epsilon }\perp \mathbf{c}$) and TM ($\overrightarrow{\epsilon }\parallel \mathbf{c}$) polarized polariton modes in the ZnO microcavity are shown. Dashed curves: Theoretical fittings for the lower polariton branches. The photon emitted at angle $\varphi$ carries the polariton energy $E$ and its wave vector component $k_{\parallel }=(E/\hslash c)\sin \varphi$.

Figure 2

Room-temperature $\mathit{k}$-space PL mapping under high excitation. (a) Polariton lasing in the 1D microcavity with pumping power $P=0.33\mu \mathrm{W}$. The intensity has been color scaled in logarithm. (b) Polariton nonlinear scatterings with pumping power $P=1.30\mu \mathrm{W}$. (c) Schematic picture for the PPS process, $\{[E,\mathit{k}(0)],[E,\mathit{k}(0)]{\}}_N\to \{[E,\mathit{k}(\varphi )],[E,\mathit{k}(-\varphi )]{\}}_{N-1}$.

Figure 3

(a) $\mathit{k}$-space PL mappings under four different pumping powers. (b) Scattering probabilities at positions $A,B,C$ as a function of the intensity of the polariton scattering source. $B$: Scattering to the $N=47$ polariton mode, $A$ and $C$: Off-resonance scatterings. (c) The similar scattering behavior between polariton modes $N=47$ and $N=46$.

Figure 4

(a) Sketch for the dynamics of the PPS process. (b) Theoretical fitting for the scattering between modes $N=48$ and $N=47$. The red diamonds (green circles) represent the dependence of the scattered polariton signal $I_S$ (idler $I_I$) on the scattering source $I_0$. The blue line is the fitting of the PPS process with $\hslash {\alpha }_{\mathrm{PPS}}=1.1\times {10}^{-4}\mathrm{meV}$. (c) Similar fitting for the scattering between modes $N=47$ and $N=46$ with $\hslash {\alpha }_{\mathrm{PPS}}=0.3\times {10}^{-4}\mathrm{meV}$. The polariton-disorder scattering coefficients $\hslash {\alpha }_{\mathrm{linear}}$ for these two scattering processes are of the order of ${10}^{-2}\mathrm{meV}$.