Single-mode Polariton Laser in a Designable Microcavity

Transcription

1 Single-mode Polariton Laser in a Designable Microcavity Hui Deng Physics, University of Michigan, Ann Arbor Michigan Team: Bo Zhang Zhaorong Wang Seonghoon Kim Collaborators: S Brodbeck, C Schneider, M Kamp, S Hoefling University of Wuerzburg

2 Single-mode Polariton Laser in a Designable Microcavity What is semiconductor microcavity polariton Why designable cavity with a photonic crystal mirror Single-mode, 0D polariton laser in a designable cavity Coherence properties Summary

3 Weak & Strong Coupling γ κ weak coupling g < γ, κ strong coupling g >> γ, κ 10 mev <1 mev, Q>10 3

4 Microcavity Polaritons photon exciton HH = Σ kk [EE ppp kk aa kk + aa kk + EE eeeeee kk ee kk + ee kk +gg 0 (aa + kk ee +aa kk ee + )] dipole-coupling κ strong coupling g >> γ, κ 10 mev <1 mev, Q>10 3 γ HH = ΣΣ kk EE pppppp kk pp + kk pp kk Polariton: pp kk = uu kk aa kk + vv kk ee kk EE pppppp kk = 1 2 [EE ppp kk + EE eeeeee kk ] ± gg EE ppp (kk) EE eeeeee (kk) 2 /4 pp kk, pp + kk = 1 + OO(nn eeeeee )

5 Microcavity Polaritons photon exciton HH = Σ kk [EE ppp kk aa kk + aa kk + EE eeeeee kk ee kk + ee kk +gg 0 (aa + kk ee +aa kk ee + )] dipole-coupling γ HH = ΣΣ kk EE pppppp kk pp kk + pp kk Polariton: pp kk = uu kk aa kk + vv kk ee kk κ strong coupling g >> γ, κ 10 mev <1 mev, Q>10 3 robust against local defects direct experimental access strong nonlinearity rich manybody physics

6 2D Polariton Lasing and Condensation Quantum Degeneracy k-space occupancy & distribution Deng et al, Science 298, 5591 (2002); Deng et al, PNAS 100, (2003); Kasprzak et al, Nature 443, 409 (2006); Coherence Functions 1st order spatial coherence (p ) Richard, et al, PRL 94, (2005); Deng, et al, PRL 99, (2007)... Long-Range Transport, Vortices, Josephson Oscillations, Pattern Formation 1 st & 2 nd order temporal coherence Deng et al, Science 298, 5591 (2002); Kasprzak, et al, PRL 100, (2008); Love, et al, PRL 101, (2008) Lagoudakis, et al, Nat Phys 4, 706 (2008); 1.5 Amo, et al, Nature 457, 291 (2009); Sanvitto, et al, Nat Phys 6, 527 (2010) time (ns) time (ns) g (2) (0) P/P th = 1 Pump Rate P/P th P/P th = 15

7 Polariton vs Atom: Fundamental Science Relaxation time: ps vs. 1 ms Lifetime: ps vs. 1 s Non-equilibrium, open system universality of physics unique features Δμμ/gg dissipative branch θθ ( kk) Goldstone modes Szymańska et al. PRL 96, (2006) g (2) (0) gg 1 P/P th = time (ns) Deng 2002 xx xx 1 Roumpos 2011 gg 2 ττ = 0 ~1.4 P/P th = time (ns) Pump Rate P/P th

8 Polaritons vs. Atoms: Applications High T c (4K-350K) m*~10-8 m H Built-in matter-light interface Semiconductor platform Tunability Integration, Scalability Polariton Laser w/o Population Inversion Ultrafast Switches Cerna K (GaAs, CdTe) 300K (GaN, ZnO, organics) Electrical Pumping polariton, E lp = ev cavity mode, E cav = ev 10 0 no electronic inversion with inversion Deng 2003 Das 2011 Schneider 2013 Bhattacharya 2013, 2014

9 Polariton Quantum Devices Matter-wave Circuits Kavokin, Liew, Savona, Shelykh... Quantum Light Generation Liew 2008 Liew 2010 Novel Phases & Q. Simulation Carusotto, Fazio, Hartmann, Hollenberg, Koch, Lukin, Plenio, Tureci,... Tureci Liew 2011

10 A New Era: Confine, Control & Couple Polariton Quantum Fluids non-equilibrium physics applications quantum devices

11 Control, Confine, Couple 1. Via the Excitons Mechanical strain potential (Snoke, Pittsburg) External E&M fields (Larionov PRL) Optical stark effect (Steinberg, Toronto) Exciton interactions/saturation (Baumberg, Cambridge; ) 2. Change the Cavity Surface patterning(yamamoto, Stanford) Balili 2007 Tosi 2012 Kim 2011 Protected excitons & coherence Weak confinement /modulation of polaritons Embedded apertures (Deveaud, EPFL; Hoefling, Wuerzburg) 0D/1D polaritons Etching (1D, 0D, 2 joint 0D/1D) (Bloch, LPN/CNRS; Hoefling, Wuerzburg) Kaitouni 2006 Bajoni 2008 Exciton loss Spurious free carriers Complex Tech.

12 A Sandbox Polariton System? 1. Strong lateral confinement 2. Non-destructive to excitons 3. Control of the Fundamental Properties Dispersion, energy DOS, group velocity Polarization/angular-momentum 4. Coupling & Integration Coupled 0D/1D arrays Hybrid-dimensional systems Integrate with other polaritonic & photonic elements 5. Additional Flexibilities: reservoir engineering, in-situ tuning, opto-mechanical couplings,

13 DBR-DBR Microcavity... Bottom DBR of ~20λλ QW exciton Top DBR of ~20λλ

14 DBR-DBR Microcavity... Bottom DBR of ~20λλ QW exciton Top DBR of ~20λλ DBR of 7λλ Exciton Cavity layer thickness ~λλ/22 DBR thickness: λ Q = for perfect structure Epitaxial grown over 1-2 days

15 A Different Cavity Architecture HCG: Sub-Wavelength High Index Contrast Grating Reflectance DBR PC Grating Wavelength λ (nm) Cavity Quality Factor Q HCG-DBR HPCC (1.25λ top mirror) DBR-Cavity Thickness of Top DBR (λ)

16 HCG-DBR Cavities ηλ Λ d 1 d 2 Applications to passive elements Fattal, et al, Nat Photon 4, (2010). Establish strong- coupling Applications Establish to VCSELs lasing/condensation Huang et al, Nat Photon 1, 119 (2007). Zhou, et al, IEEE Quant Elec. 15, 1485 (2009) Applications to Polaritons 1/10 of DBR thickness Higher reflectance Broader stopband width Tunable air gap Design flexibility of PC Controlling the photon directly controls the polariton Lower dimensions and coupled polariton systems Polarization selectivity Dispersion engineering Dynamic tuning of the resonances

17 0D Polariton in a HCG-DBR Cavitry

18 A 0D SWG-DBR Cavity SEM cross section Zhang et. al., Light Sci Appl 3, e135 (2014) SEM Top view

19 3D Confinement Discrete TE Modes within a 7.5 um HCG Continuous Excitons on the planar device E exc Zhang et. al., Light Sci Appl 3, e135 (2014)

20 k & r wavefunctions k-space mode structure r-space mode structure Zhang et. al., Light Sci Appl 3, e135 (2014) x (um)

21 Polariton Dispersion EE UP Cavity Photon (mm ppp ~10 5 mm ee, ττ ppp ~10 ps) QW Exciton (mm eeeeee ~10 1 mm ee, ττ eeeeee ~1 ns) kk LP (mm LLLL ~ 2mm ppp ~ 10 5 mm ee, ττ LLLL ~ 2ττ ppp ~ 10 ps )

22 Zhang et. al., Light Sci Appl 3, e135 (2014) Polariton Dispersion

23 Polariton Dispersion UP E UP (k=0) = ev Exciton: ev Measured by planar/tm exciton LP E LP (k=0) = ev Zhang et. al., Light Sci Appl 3, e135 (2014) Calculate: cav E c (k=0) = ev; g 0 = 11.8 mev Confinement: Harmonic potential for the cavity photon

24 Temperature Tuning Cavity calibrated by reflectance of planar devices LP, <k>=0 mode k-space PL or reflectance g 0 ~ 11 mev Exciton measured by PL of planar devices Zhang et. al., Light Sci Appl 3, e135 (2014)

25 Zhang et. al., Light Sci Appl 3, e135 (2014) 0D Polariton Lasing

26 0D Polariton Lasing P th P th P th Zhang et. al., Light Sci Appl 3, e135 (2014)

27 Polarization TE Discrete LP TM Flat-Band Exciton

28 Polarization TE k=0 TM k=0 TE TM Zhang et. al., Light Sci Appl 3, e135 (2014)

29 A Perfect Polariton Laser in 2 nd -order coherence

30 Second-Order Coherence Function g ( 2) : n( t) n( t + τ ) : ( τ ) = 2 n g (2) (0) = 2, thermal/chaotic = 1, coherent < 1, non-classical state g (2) (0)=1.25

31 What Affects g (2)? Kinetics of weakly interacting Bosons g (2) =1 Not observed in 2D polaritons Deng 2002, Kasprzak 2006, Love 2008, Horikiri 2010, Aβmann PNAS 2011, Rahimi-Iman Reservoir Love 2008, Whittaker Mode competition 2D condensates are (always) fragmented Simultaneous competition among k-modes, polarizations & spatial modes Can NOT select single mode in 2D Exp: Aβmann PNAS 2011, Kusudo Condensate non-resonant scattering quantum depletion & phase locking Intrinsic, but how large? Hard to control or measure Theories: Schwendimann & Quattropani 2008, 2010, Haug D polaritons Multiple effects Multiple lasing modes Hard to Separate/control

32 Second-Order Coherence Bunching below P th pulsed CW 1 st 0 th g (2) (0) Sharpe decrease at P th Full coherence above P th P/P th Kim et. al., Coherence of a Single-Mode Polariton Laser, in preparation NO mode-competition or condensate fragmentation Single polarization Discrete k-modes No random spatial localization Suppressed non-resonant scattering

33 What Affects g (2)? Kinetics of weakly interacting Bosons g (2) =1 Not observed in 2D polaritons Realized in 0D HCG-DBR polaritons Deng 2002, Kasprzak 2006, Love 2008, Horikiri 2010, Aβmann PNAS 2011, Rahimi-Iman Reservoir Does not affect g (2) Can Love control/measure 2008, Whittaker 2009 via TM exciton 2. Mode competition Simultaneous competition among k-modes, spatial modes & polarizations 2D condensates are (always) fragmented Can NOT select single mode in 2D Exp: Aβmann PNAS 2011, Kusudo 2013 Can be turned off and/or controlled 3. Condensate non-resonant scattering quantum depletion & phase locking Unavoidable Hard to control or measure Can be turned off and controlled Theories: Schwendimann & Quattropani 2008, 2010, Haug D HCG-DBR different effects can be separately turned-off and/or controlled/measured 2D polaritons Multiple effects Multiple lasing modes Hard to Separate/control

34 Cross-Correlation & Virtual-Scattering Ground state 1 st excited state NO modecompetition g (2) (0) cross-correlation anti-correlation Virtual scattering from condensate P/P th Kim et. al., Coherence of a Single-Mode Polariton Laser, in preparation

35 With Two-Mode Competition Ground state 1 st excited state 10 3 g (0) Intensity (Arb Units) P/P th STRONG two-mode competition P/P Kim et. al., Coherence of a Single-Mode th Polariton Laser, in preparation small increase in g (2) small decrease in g c (2)

36 Dispersion Engineering HCG1 DBR HCG2 HCG3 Wang et. al., Dispersion Engineering of a Vertical Microcavity, in preparation

37 from Localization to Coupling Decoupled Cavities Localizd Mode Coupled Cavities Discrete Modes Coupled Cavities Band Structures 2 cells, 15 µm apart 3 cells, 7.5 µm apart 9 cells, 7.5 µm apart kk (µm 1 ) xx xx kk Zhang et. al., Photonic Potential of Polaritons by Strain Engineering, in preparation

38 A Sandbox Polariton System 1. Strong polariton confinement 2. Non-destructive to excitons Strong Coupling 3D Confinement Single mode laser gg (2) (0) = 1 3. Control the Fundamental Properties 4. Coupling & Integration 5. Additional flexibilities: reservoir engineering, in-situ tuning, optomechanical couplings, hybrid materials

39 Acknowledgements Seonghoon Kim Bo Zhang Zhaorong Wang SPONSORS COLLABORATORS HÖfling Group Würzburg, Germany