1 II-VI semiconductor microcavities microcavity physics polariton stimulation prospects

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

3 cavity mode exciton k z1, k // k z2, k //  Rabi Selection rule : conservation of in-plane wavevector k // exciton (k // )  cavity mode (same k // ) 2D light-matter interaction  cav XX  cav,,  X <  Rabi strong coupling regime : polaritons > weak coupling regime : Purcell effect UP LP

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

5 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 // Polariton features

6 II-VI VS III-V Lattice mismatch

7 GaAs CdTe ZnSe Oscillator strength (x cm -2 ) Rabi splitting ~ 6 meV 4 QWs one QW Exciton binding energy (meV) screening density (x cm -2 ) 10 II-VI microcavities well suited for polariton condensation II-VI VS III-V

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  P 2 ! 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 AndréRobert RomestainLe Si Dang Maxime Richard (PhD)Jean-Michel Gérard Kuntheak Kheng Henri Mariette Yvan Robin (PhD) Sebastian Moehl (PhD)