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- Condensation of polaritons up to 300K and in-plane propagation in a ZnO microcavity hal link

Auteur(s): Guillet T., Li Feng, Orosz Laurent, Kamoun O., Bouchoule Sophie, Brimont C., Disseix Pierre, Lafosse Xavier, Leroux Mathieu, Leymarie Joël, Malpuech Guillaume, Mexis M., Mihailovic Martine, Patriarche Gilles, Réveret François, Solnyshkov Dimitri, Zúñiga-Pérez Jesús

Conference: 13th international conference on Optics of Excitons in Confined Systems (OECS13) (Rome, IT, 2013-09-09)


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Résumé:

ZnO is a wide bandgap semiconductor with strong excitonic properties, in particular a large oscillator strength and a large exciton binding energy. It therefore raises a strong interest for the generation and control of polariton condensates up to room temperature. We have recently reported the condensation of polaritons in a bulk ZnO microcavity over an unprecedented range of exciton-photon compositions and of temperatures, up to room temperature [1]. The complete phase diagram of the ZnO polariton laser has been measured (cf figure 1a), showing that its threshold is only 6 times larger at 300 K than at 8 K. It is in a good qualitative agreement with the simulations of exciton and polariton relaxation in a kinetic model (figure 1b). Strongly excitonic (96% exciton fraction) as well as strongly photonic condensates (83% photon fraction) are realized (figure 1c). Moreover imaging of the condensate allows to evidence in-plane free propagation of the polariton condensate starting from the excitation spot. This tunability is obtained on a fully-hybrid microcavity with a high quality factor (Q>2000) and a large Rabi splitting (250 meV); it represents an important progress compared to our previous demonstration of a ZnO polariton laser in a Q=450 microcavity [2], as well as to other recent reports [3]. It also confers a strong advantage to ZnO microcavities compared to GaN [4], since strong excitonic condensates can here be investigated. Figure 1. (a) Detuning dependence of the polariton condensation threshold for a 2.5 polariton branch, under quasi-continuous excitation; (b) Polariton density at the condensation threshold deduced from the kinetic model; (c) Angle-resolved emission below and above threshold (T=300K, almost zero detuning). The authors acknowledge financial support from FP7 program through ITN networks CLERMONT4 (235114) and SPIN-OPTRONICS (237252). References [1] F. Li et al., Phys. Rev. Lett. 110, 196406 (2013) [2] T. Guillet et al., Appl. Phys. Lett. 98, 211105 (2011) [3] H. Franke et al., New J. Phys. 14, 013037 (2012); T.C. Lu et al., Optics Express 20, 5530 (2012) [4] J. Levrat et al., Phys. Rev. B 81, 125305 (2010)