ii-vi semiconductor microcavities
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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II-VI semiconductor microcavities
• microcavity physics
• polariton stimulation
• prospects
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z
QW ~ 10 nm optical cavity ~ 1 µm
Semiconductor microcavity
Confinement along z for both cavity modes and QW excitons
2D light-matter interaction
mirror
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cavity mode exciton
kz1, k// kz2, k//
Rabi
Selection rule : conservation of in-plane wavevector k//
exciton (k//) cavity mode (same k//)
2D light-matter interaction
cav X
cav ,, X < Rabi strong coupling regime : polaritons
> weak coupling regime : Purcell effect
UP
LP
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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
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• 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
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II-VI VS III-V
• Lattice mismatch
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GaAs CdTe ZnSe
• Oscillator strength (x 1013 cm-2 ) 0.6 2.3
Rabi splitting ~ 6 meV 4 QWs one QW
• Exciton binding energy (meV) 10 25 40
screening density (x 1011 cm-2 ) < 1 5 > 10
II-VI microcavities well suited for polariton condensation
II-VI VS III-V
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Probe of polariton population
PL measured at different angles to the microcavity normal
24 QWs
T = 4K
+ 5 meV
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II-VI VS III-V Probe of polariton population
N PL
Bottleneck effect
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Polariton stimulation
Non-resonant quasi-cw excitation
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Polariton stimulation
polariton-polariton scattering P2 !
Bosonic final state stimulation
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Polariton stimulation
Suppression of bottleneck effect
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Polariton stimulation
New polariton dispersion above stimulation threshold
Evidence of macroscopic coherence ?
(Ciuti, PRB 2001)
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Resonant excitation : parametric gain
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Parametric gain : II-VI VS III-V
M. Saba et al., Nature 2001
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Parametric gain : II-VI VS III-V
M. Saba et al., Nature 2001
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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 ?
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Microcavity activities in Grenoble
Polariton stimulation Single 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)