Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)

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Accueil > La Recherche > Axes & Equipes > Physique de l’Exciton, du Photon & du Spin > Optique des états collectifs et des spins (OECS) > Etats collectifs dans les semiconducteurs > Condensats de polaritons et lasers à polaritons dans les microcavités GaN, ZnO

ZnO Microcavities

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Excitons in wide band gap semiconductors, and especially ZnO, present binding energies and oscillator strength one order of magnitude larger than GaAs. Our theoretical predictions in 2002 have shown that the strong coupling in ZnO microcavities can be robust up to room temperature, with specificities recently investigated in our group.
Within the ANR project ZOOM, coordinated by our group (in collaboration with CRHEA, LASMEA and LPN), this strong coupling has been demonstrated at 300K. Our prospect is to demonstrate the feasibility of a ZnO polariton laser, so that we now turn to the optimization of the cavity quality factor, and the understanding of the microcavity emission under strong photo-excitation.
This studies benefit from the strong experimental potential developed in the group over the past years, and initially dedicated to the study of the recombination dynamics in wide band gap heterostructures (time-resolved spectroscopy), and to the spectroscopy of individual quantum dots (home-made UV-dedicated microphotoluminescence). A specific goniometer has also been set up for angle-resolved spectroscopy.

Signatures of strong exciton-photon coupling in a ZnO microcavity. The polariton modes based on Bragg and cavity photon modes are visible in reflectivity and photoluminescence spectroscopy. As the thickness of the ZnO active layer is varied, they present an anti-crossing at the energy of the ZnO A and B excitons (3.37eV at 10K).Collaboration with CRHEA, LASMEA, LPN – ANR ZOOM [S. Faure et al., Appl. Phys. Lett. 95, 121102 (2009)] - © L2C
Non-linear relaxation of exciton-photon polaritons in a ZnO microcavity, in the strong coupling regime at 300K. Under strong photo-excitation (blue circle), the polariton modes based on Bragg and cavity photon modes partially relax towards low energy states (yellow circles). This process is directly monitored when measuring the polariton emission as a function of the emission angle, i.e. their in-plane wave-vector. Collaboration with CRHEA, LASMEA, LPN – ANR ZOOM [S. Faure et al., Appl. Phys. Lett. 95, 121102 (2009)] - © L2C
Comparison between simulated reflectivity spectra of analogous GaAs, GaN and ZnO microcavities in the strong exciton-photon coupling regime. S. Faure et al., Phys. Rev B 78, 235323 (2008) - © L2C

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