Snapshot Angle-Resolved Spectroscopy and Its Application for Study of Highly Efficient Polariton OLEDs

The multifunctional snapshot angle-resolved spectroscopy (ARS) system capable of electroluminescence, photoluminescence, and reflectance measurements for thin film devices is developed based on the k-space imaging technique. Compared with the conventional goniometric ARS system, this snapshot spectroscopy system offers great advantages of rapid and simple measurement, suitable for characterizing thin film devices that are unstable or degraded under long-time or high-power driving conditions, such as OLEDs. We perform a detailed calibration of the snapshot system and show that the measured results closely match with those obtained using a goniometric system. Furthermore, we show the capabilities of the system with application in studying polariton OLEDs. The result provides comprehensive information on the polariton mode dispersion and emission distribution, and shows an effective radiative pumping of the lower polariton branch for high emission efficiency.

Динамика спинорной экситон-поляритонной системы в латерально сжатых GaAs микрорезонаторах при резонансном фотовозбуждении

The evolution of the spatial coherence and the polarization has been studied in a freely decaying polariton condensate that is resonantly excited by linearly polarized picosecond laser pulses at the lower and upper sublevels of the lower polariton branch in a high-Q GaAs-based microcavity with a reduced lateral symmetry without excitation of the exciton reservoir. It is found that the condensate inherits the coherence of the exciting laser pulse at both sublevels in a wide range of excitation densities and retains it for several dozen picoseconds. The linear polarization of the photoexcited condensate is retained only in the condensate at the lower sublevel. The linearly polarized condensate excited at the upper sublevel loses its stability at the excitation densities higher a threshold value: it enters a regime of internal Josephson oscillations with strongly oscillating circular and diagonal linear degrees of polarization. The polariton–polariton interaction leads to the nonlinear Josephson effects at high condensate densities. All the effects are well described in terms of the spinor Gross–Pitaevskii equations. The cause of the polarization instability of the condensate is shown to be the spin anisotropy of the polariton–polariton interaction.

Polarization behavior of the exciton-polariton emission of ZnO-based microresonators

We present the polarization behavior of the exciton-polariton luminescence of a ZnO-based all-oxide resonator. A splitting in the emission energy between the s- and p-polarized pho-toluminescence of the lower polariton branch was observed which increases with increasing emission angle. It is caused by the polarization behavior of the uncoupled cavity-photon mode, and reaches a maximum of about 5 meV at an emission angle near the bottleneck region. For lar-ger angles the energy splitting decreases. Additionally to the energy splitting, we observed dif-ferences in the photoluminescence intensity which we trace back to different occupation of the lower polariton branch for the two polarizations. Whereas for p-polarization a bottleneck effect is clearly observable, this effect is much weaker for s-polarization. These findings indicate that the relaxation of hot carriers into the bottleneck region is enhanced for the p-polarized photolumi-nescence compared to the s-polarized one. The differences between these two polarizations are most pronounced for a very large negative detuning and vanish with increasing detuning.