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II-VI semiconductor microcavities

II-VI semiconductor microcavities. microcavity physics polariton stimulation prospects. Semiconductor microcavity. z. mirror. optical cavity ~ 1 µm. QW ~ 10 nm. Confinement along z for both cavity modes and QW excitons 2D light-matter interaction.

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II-VI semiconductor microcavities

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  1. II-VI semiconductor microcavities • microcavity physics • polariton stimulation • prospects

  2. Semiconductor microcavity z mirror optical cavity ~ 1 µm QW ~ 10 nm Confinement along z for both cavity modes and QW excitons 2D light-matter interaction

  3. Selection rule : conservation of in-plane wavevector k// exciton (k//)  cavity mode (same k//) 2D light-matter interaction UP cavity mode exciton kz1, k// kz2, k// cav Rabi X LP cav ,, X < Rabi strong coupling regime : polaritons > weak coupling regime : Purcell effect

  4. Polariton in-plane dispersion Cavity mode confined along z : k1z ~ 8.106 m-1 >> k// photon dispersion >> exciton dispersion photon mass ~ 10-4 exciton mass Polariton = photon * exciton polariton DOS ~ 10-4 exciton DOS

  5. Polariton features • finite lifetime  1 ps (mirror reflectivity) • high radiative recombination rate • k//  • k// = ( / c) sin • direct injection / probe of polariton population • LP = trap in k space with small DOS • macroscopic state occupancy can be achieved for densities well below the exciton screening limit • bosonic final state stimulation  Bose condensation z  k//

  6. II-VI VS III-V • Lattice mismatch

  7. II-VI VS III-V • GaAsCdTe ZnSe • Oscillator strength (x 1013 cm-2 ) 0.6 2.3 • Rabi splitting ~ 6 meV 4 QWs one QW • Exciton binding energy (meV) 1025 40 • screening density (x 1011 cm-2 ) < 1 5 > 10 II-VI microcavities well suited for polariton condensation

  8. Probe of polariton population PL measured at different angles  to the microcavity normal 24 QWs T = 4K   + 5 meV

  9. II-VI VS III-V Probe of polariton population N  PL  Bottleneck effect

  10. Polariton stimulation Non-resonant quasi-cw excitation

  11. Polariton stimulation polariton-polariton scattering  P2 ! Bosonic final state stimulation

  12. Polariton stimulation Suppression of bottleneck effect

  13. Polariton stimulation New polariton dispersion above stimulation threshold Evidence of macroscopic coherence ? (Ciuti, PRB 2001)

  14. Resonant excitation : parametric gain

  15. Parametric gain : II-VI VS III-V M. Saba et al., Nature 2001

  16. Parametric gain : II-VI VS III-V M. Saba et al., Nature 2001

  17. Prospects • Polariton stimulation under non-resonant excitation conditions at RT ? • Larger exciton binding energy, e.g. in ZnSe, GaN, organic microcavities • Deeper trap / scattering efficiency ?

  18. Microcavity activities in Grenoble Polariton stimulationSingle photon solid source (2D microcavity + QW) (0D microcavity + QD) Régis André Régis André Robert Romestain Robert Romestain Le Si Dang Le Si Dang Maxime Richard (PhD) Jean-Michel Gérard Kuntheak Kheng Henri Mariette Yvan Robin (PhD) Sebastian Moehl (PhD)

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