Optically Controlled Femtosecond Polariton Switch at Room Temperature

Exciton polaritons have shown great potential for applications such as low-threshold lasing, quantum simulation, and dissipation-free circuits. In this paper, we realize a room temperature ultrafast polaritonic switch where the Bose-Einstein condensate population can be depleted at the hundred femtosecond timescale with high extinction ratios. This is achieved by applying an ultrashort optical control pulse, inducing parametric scattering within the photon part of the polariton condensate via a four-wave mixing process. Using a femtosecond angle-resolved spectroscopic imaging technique, the erasure and revival of the polariton condensates can be visualized. The condensate depletion and revival are well modeled by an open-dissipative Gross-Pitaevskii equation including parametric scattering process. This pushes the speed frontier of all-optical controlled polaritonic switches at room temperature towards the THz regime.

Figure 1

(a) The experimental scheme. (b) Schematic energy-momentum dispersion for the ZnO microwire. Two photons from the 700 nm control pulse induce stimulated scattering from the polariton condensate formed at around $k_{//}=0$ on the LP branch. The idler photon is at a long wavelength of $3.4\mu \mathrm{m}$. (c) The integrated angle-resolved PL spectrum obtained at 350 nm at the pump fluence of about $7.0\times {10}^{-4}\mathrm{J}/{\mathrm{cm}}^2$. The pump fluence dependence of (d) the ground-state occupation, the emission linewidth, and (e) the energy at the maximum of the PL emission spectra. (f) The integrated angle-resolved PL spectrum obtained for excitation at 700 nm at the fluence of $3.4\times {10}^{-3}\mathrm{J}/{\mathrm{cm}}^2$.

Figure 2

Control pulse delay dependence of polariton condensate population for fixed control power. The pump power is $\sim 6{\mathrm{P}}_{\mathrm{th}}$. The fluence of the control pulse is about $2.9\times {10}^{-3}\mathrm{J}/{\mathrm{cm}}^2$. (a) The time-resolved, momentum-integrated PL spectra. The integrated signal from all the LP branches to the time axis with (b) no control pulse, control pulse with delay at (c) 1.7, (d) 2.3, (e) 3.0, and (f) 4.5 ps. The duration and the arrival time of the control pulses are indicated by the gray areas.

Figure 3

Control pulse power dependence of polariton condensate population for fixed control pulse delay at 2.4 ps. Color images shown are the time-resolved, momentum-integrated PL spectra. The pump power is $\sim 6P_{\mathrm{th}}$ for all cases with (a) no control pulse, control pulse fluence at (b) $2.3\times {10}^{-3}\mathrm{J}/{\mathrm{cm}}^2$, (c) $3.4\times {10}^{-3}\mathrm{J}/{\mathrm{cm}}^2$, (d) $5.7\times {10}^{-3}\mathrm{J}/{\mathrm{cm}}^2$. The blue curves represent the integrated signal from all the LP branches. The blue arrows indicate the times where the polariton is switched off. The black arrow in (c) indicates the 6 orders of magnitude (OOM) difference between the “on” and the “off” states.

Figure 4

Numerical simulation of the optical switch using an open-dissipative Gross-Pitaevskii equation. (a) Comparison of the simulated and the experimentally measured polariton signal obtained from the data shown in Fig. 3. (b) The calculated dynamics for polariton condensation and the parametric scattering process for the various participating modes as labeled. (c) Effect on polariton revival as a function of control pulse intensity.