Polariton laser in micropillar cavities D. Bajoni, E. Wertz, P. Senellart, I. Sagnes, S. Bouchoule, A. Miard, E. Semenova, A. Lemaître and J. Bloch Laboratoire de Photonique et de Nanostructures LPN/CNRS, Marcoussis, France Outline 2D GaAs cavities : polariton laser or photon laser? D polariton states in micropillars Polariton laser: D versus 2D OPO with D polariton modes Polariton electrical injection
Motivations Cavity polaritons : exciton photon mixed state Strong χ 3 non linearities : OPO (Savvidis PRL2, Stevenson PRL2, C. Diederich Nature2 ) > generation of correlated photon pairs 1.47 upper polariton photon exciton 1.47 lower polariton 4 C. Weisbuch et al., PRL 92 Bosonic statistic : macroscopic occupation of a quantum state BEC (J. Kasprzak Nature2, R. Balili Science27, C. W. Lai Nature27) Polariton laser: Low threshold source of coherent light (S. Christopoulos PRL27, D. Bajoni PRL28) 1 k // (cm )
Reports of Bosonic effects in semiconductor microcavities II VI (CdTe) : Non resonant excitation, Low temperature J. Kasprzak Nature2 GaN: Non resonant excitation, 3 K S. Christopoulos PRL27, G. Christmann APL 28 GaAs: Low temperature Non resonant excitation Trap in real space, R. Balili et al., Science 27 Resonant excitation, 2D Deng et al., Science 22, PRL 27 C. W. Lai,et al., Nature 27
Polariton relaxation under non resonant excitation cw non resonant Pump: high energy electron hole pairs Energy ) 1 + f ( Bosonic stimulation: Γ relaxation (f+1) f 4 2 1 k // (µm ) 2 4 f >>1 : quantum degeneracy; coherence. But we need : Polariton lifetime >> Polariton relaxation time! Relaxation bottleneck
Polariton relaxation under non resonant excitation! Relaxation bottleneck, polariton polariton scattering to enhance polariton relaxation Tartakovskii, PRB 2, Senellart PRB 2! Exciton screening at high excitation density : strong coupling > weak coupling R. Houdré, PRB 199, R. Butté PRB 22 Screening of the strong coupling regime, electron hole plasma in the weak coupling regime Vertical Cavity Surface Emitting Laser We need high occupation factors for a moderate total exciton density
Large Rabi splitting GaAs microcavity: 2D Large number of quantum wells Total saturation density N x (one QW saturation density) Overcome relaxation bottleneck? 1 1 pairs 2 pairs Energy (m ev) 3 x 4 GaAs QW 13 12 J. Bloch, APL (1998) HH 1 1 Ω 19 18 14 Same structure as Yamamoto et al. Snoke et al. LH 14 13 12 HH 1 mev 11 Position (mm)
Large Rabi splitting GaAs microcavity: 2D cw Emission at k// Energy at threshold Cavity mode
Large Rabi splitting GaAs microcavity: 2D cw Angle resolved photoluminescence δ 1. mev cavity m ode redshifted cavity m ode H H exciton 11 Lower polariton 1 P 2.2 P th P.3 P th..x 1 In plane wavevector (m )
Large Rabi splitting GaAs microcavity: 2D cw Angle resolved photoluminescence δ 1. mev cavity m ode redshifted cavity m ode H H exciton 11 Dispersion of a cavity mode Lower polariton 1 P 2.2 P th P.3 P th.. x 1 In plane wavevector (m ) Carrier induced refractive index renormalization Regular photon lasing! Too high carrier density
Large Rabi splitting GaAs microcavity: 2D Intensity distribution of the photon laser PL integrated Intensity (arb.u.) δ 1. mev 8 7 4 3 P2.2 P th cw Similarities between photon laser and polariton condensate P.3 P th 1 2 3 4 E E min (m ev) D. Bajoni et al., Phys. Rev. B 7, R213 (27)
Large Rabi splitting GaAs microcavity: 2D New generation of samples : higher finesse Q > 12 1 pairs 2 pairs 3 x 4 GaAs QW 2 pairs 3 pairs (mev) Energy 1 1 Energy at threshold 14 14 Ω 12 12 1 1 2 2 HH 1 mev Strong coupling?! 2 2 1 1 Detuning Detuning(meV) (mev) 1 1
E Selective probe (emission or excitation) of the polariton states z θ k ( cm émission(θ ) θ k (4 cm 1) ) k ω /c sin(θ ) k
Large Rabi splitting GaAs microcavity: 2D New generation of samples : higher finesse 9 8 7 4 3 2 4 m W 3 m W 2 m W m W m W 2 m W 1 m W 12 m W m W 9 mw 8 mw 7 mw mw mw 2 mw 1 mw. m W 1 11 12 12 Energy (m ev) 13 Integrated Intensity (a.u.) Integrated Intensity (a.u.) δ +. mev 11 9 8 7 4 3 2 1 Pump Power (mw )
Large Rabi splitting GaAs microcavity: 2D New generation of samples : higher finesse 1E8 δ +. mev P P th 1E7 13 1 1 12 13 14 1E8 P 1E7 P th P Pth P Pth P.2 Pth 12 1 1 12 13 14 12 2x 1E8 P.2 P th 1E7 1 1 12 13 14 1x 1x 2x 1 k // (m ) 3x 4x x
Large Rabi splitting GaAs microcavity: 2D New generation of samples : higher finesse δ +. mev 9 P P th P P th P,2 P th 8 7 T 4 K Occupancy (a.u.) 13 P Pth P Pth P.2 Pth 12 12 4 2x 2 4 E E min (mev) 1x 1x 2x 1 k // (m ) 3x 4x x
Large Rabi splitting GaAs microcavity: 2D New generation of samples : higher finesse Polariton lifetime >> relaxation time Build up of a large occupancy at k in the strong coupling regime Polariton laser (BEC?) in a GaAs 2D microcavity under NON RESONANT excitation Lateral confinement : D polariton states in the same sample Discussion of 2D versus D for polariton lasing
Photon modes in a micropillars Photons confined along z: kz pπ /Lc Photons confined along x and y: refractive index contrast between air and semiconductor kx pxπ /Lx ky pyπ /Ly Ly Lx Lc << Lx,Ly 194 192 Discrete spectrum : px and py 19 188 18 2 184 EPx, py 182 18 178 17 1. 2. 2. 3. 3. 4. 4. size ( µm)... 2 c pπ p xπ p yπ + + n Lc Lx Ly 2
Exciton Photon coupling in micropillars Photon modes Exciton enveloppe function : p yπ y p xπ x E p x, p y ( x, y ) sin( ) sin( ) Lx Ly p yπ y p xπ x ψ px, p y ( x, y ) sin( ) sin( ) Lx Ly One to one coupling between exciton and photon modes (for lateral size > 2 µm) Ex px, py g g EC px, py G. Panzarini and L. C. Andreani, PRB, 1799 (1999) > Exciton photon mixed states Discrete polariton states
D polariton states in micropillars Fabrication : Electron beam lithography Reactive ion etching 2 pairs 2 2 µm 3 x 4 GaAs QW 3 pairs Cavity wedge > detuning 2 µm
D polariton states in micropillars Microphotoluminescence on a single micropillar PL Intensity (arb. units) 3 Discrete Circular pillar Polariton M odes diameter4 µm M1 M2 M3 T K M4 2 Q>12 µm Exciton Emission 1 1 Discrete spectrum of polariton modes
Another approach for D polaritons R. Idrissi Kaitouni, et al., PHYSICAL REVIEW B 74, 1311 (2) Ounsi El Daif et al., Applied Phys. Lett. 92, 819 (28)
Polariton laser in a micropillar Non resonant optical pumping δ mev PL Intensity (arb. units) 7 µm 2. mw 2 mw 1.2 mw.8 mw.3 mw.1 mw 4 3 2 19 x4 x4 x4 x x2 199 12 1 Blueshift <. mev Strong coupling regime
Polariton laser in a micropillar Non resonant optical pumping PL Intensity (arb. units) 2. mw 2 mw 1.2 mw.8 mw.3 mw.1 mw coupling regime: 4 3 Strong Polariton laser 2 19 x4 x4 x4 x x2 199 µm 7 mw mw 3 mw mw 2. mw 4 PL Intensity (arb. units) δ mev 7 3 2 Weak coupling regime: Photon laser 12 1 19 199 12 1 Onset of photon lasing at higher excitation power D. Bajoni et al., Phys. Rev. Lett., 4741 (28)
Em ission energy (mev) 12 11 9 8 7 Polariton laser Photon laser 1 4 3 2 1 1 µm Measured occupancy Emission integrated intensity (arb. u.) Polariton laser in a micropillar % of the injected electron hole pairs Polariton laser 199 More than polaritons in the same quantum state 198 Photon laser 197.1 1 Excitation power (mw ) D. Bajoni et al., Phys. Rev. Lett., 4741 (28) Estimated exciton density : cm 2/QW
Em ission energy (mev) 12 11 9 8 7 Polariton laser Photon laser 1 198 Photon laser 197.1 1 4 3 2 1 1 Photon laser : non interacting bosons Polariton laser 199 µm Measured occupancy Emission integrated intensity (arb. u.) Polariton laser in a micropillar Excitation power (mw ) Polariton laser : self interaction responsible for the observed blueshift
2 Threshold (x W cm ) Polariton laser in a micropillar Photon laser 1.1 Polariton laser.1 2 4 8 12 14 1 18 2 22 Pillar size (µm ) times lower threshold!!!
Polariton laser in a micropillar PL PL intensity intensity (arb. (arb. u.) u.) Centered Centered.8 mw mw.8.7 mw.7 mw. mw mw..2 mw mw.2 1x 1x 7x 7x Edge 4x 3x 2x 1x 1.3.8.7.2 Diameter µm mw mw mw mw edge excitation: stimulation toward M2, M3 x. 3x 3x Integrated Integrated PL PL intensity intensity xx 44 1 1 1 1 x 3 1 1 Energy (m ev) Energy (m ev) 8 8 M ode1 Mode1 M ode2 Mode2 M ode3 7 7 Mode3 4 4.1.1 11.1 1 power (m W ) Excitation Excitation power (m W ) 8 7 Polariton Lasing with mode competition
Polariton laser in a micropillar: mode competition Large micropilllar Smaller micropilllar 4 µm 4 3 4x 3x 2x 1x 2 mw 1 mw Power (µw ) 17 178 18 Multimode, fragmentation Energy (ev) 1 mw 2 mw 9 8 7 4 3 4x 3x 1 mw Intensity (arb. u.) 7 x Intensity (arb. u.) x 8 Intensity (arb.u.) Integrated intensity (arb. u.) µm 2x 1x. mw Power (µw) 17 178 18 182 184 Lasing on the ground state. mw 1 mw
Mode competition: 2D versus D II VI 2D cavity Laser without power fluctuation: multimode polariton lasing Reduced dimensionality : A unique system for quantum degeneracy in a well controled quantum state
OPO with D polaritons Parametric scattering between discrete D polariton modes PL Intensity (arb. Units) 4 3 3 2 Energy conservation: Ei Ep Ep Es Square pillar 4 µm side T4K 1 s 14 Symmetry conservation: P 2 14 i 14 E 147 147 148 G. Dasbach et al., PRB 4 R2139 (21) * Pump * 4 ( r )E Pump ' ( r ) Esignal ( r ) Eidler ( r )d r
OPO with D polaritons E Px, py Energy conservation: Ei Ep Ep Es c n 2 pπ p xπ p yπ + + Lc Lx Ly (2,2) E + 8 Econf (2,1),(1,2) E + Econf (1,1) E + 2 Econf 2 2 Spectral Equidistance
OPO with D polaritons (2,2) Energy conservation: Ei Ep Ep Es (2,1) + (1,2) Symmetry conservation: * 2 * E ( r ) E ( r ) E ( r ) E ( r Pump Pump ' signal idler )d r (1,1)
OPO in micropillars 3. µm square T K Intensity (arb. u.) M1 M2 M2 M3 194 19 198 1 Energy (m ev) 12 1. x 7. x M1 Pump M3 P P P P P P 1 m W 9 m W 7 m W 1 m W 2 m W mw. 194 D. Bajoni et al., Applied Phys. Lett. 9, 17 (27) 19 198 1 12
OPO in micropillars 3. µm square T K 7 4 M2 M1 M3 Intensity (arb. u.) Integrated Intensity (a. u.) 1.x 7.x M1 Pump M3 P P P P P P 1 m W 9 m W 7 m W 1 m W 2 m W mw. 194 1 Pum p Power (mw ) 19 198 1 First observation of parametric oscillations on a single micropillar 12
OPO with microcavity polaritons Idler Signal pump idler 9 signal Pump : 17 Idler at very large angle and weakly coupled to the external field P.G. Savvidis et al. PRL 84 147 (2) R. M. Stevenson et al. PRL 8 38 (2) Micropillars Multiple cavities (collaboration J. Tignon and A. Bramati) Same intensity for signal and idler
Polariton electrical injection D. Bajoni et al., Phys. Rev. B 77, 11333 (28)
Polariton electrical injection 1482 1482 148 148 1478 1478 147 147 Log(EL intensity) Log(EL intensity) (arb. units) (arb. units) 11 22 33 44 T TKK I1 I1m maa 1474 1474 1484 1484 1482 1482 148 148 1484 1484 1478 1478 Log(EL intensity) Log(EL intensity) (arb. units) (arb. units) 33 44 T TKK I7 I7mmAA 147 147 Cavity mode 1474 1474 1472 1472 1472 1472 147 147 147 147 148 148 148 148 14 14 14 14 11 22 22 Angle Angle(degrees) (degrees) Bleaching of the strong coupling 11 22 22 Angle Angle(degrees) (degrees)
Polariton electrical injection T K Three groups : A. Khalifa et al., Appl. Phys. Lett. 92, 17 (28) T K D. Bajoni et al., Phys. Rev. B 77, 11333 (28) T K S. I. Tsintzos et al., Nature 43. 372 (28) T 23 K Further optimisation : polariton laser under electrical injection
Summary GaAs cavities : High finesse + Many QWs 7 PL Intensity (arb. units) Polariton lasing (BEC?) under non resonant excitation in 2D and in D 4 3 2 x4 x4 x4 x x2 Multimode lasing in 2D and pillars > µm 2. m W 2 mw 1.2 m W.8 m W.3 m W.1 m W 19 199 12 1 Energy (m ev) Small micropillars (< µm): quantum degeneracy of a well controlled polariton state OPO with discrete polariton states.x 148 1478 147 1484 Lo g(el intensity) (arb. u nits) 1482 1 m W 9 m W 7 m W 1 m W 2 m W mw 1 2 3 148 T K I1 m A 1474 1472. 194 19 198 1 12 1478 4 T K I7 m A 1474 1472 147 148 148 14 RTN Clermont II 3 147 147 Electrical injection of polaritons L og(el intensity) (arb. u nits) 1482 4 1.x Intensity (arb. u.) 1484 P P P P P P 7 14 1 2 Angle (degrees) 2 1 2 Angle (degrees) 2