Superradiance and Collective Atomic Recoil Laser: what atoms and fire flies have in common

1. Superradiance and Collective Atomic Recoil Laser: what atoms and fire flies have in common • Claus ZimmermannPhysikalisches Institut der Universität Tübingen

2. A.-L. Barabási, Nature 403, 849 (2000) chirping crickets applause synchronization milleniums bridge glow worms Strogatz, et. al, Nature, 438, 43-44 (2005) Self-organization pace maker cells, chirping crickets, fire flies,..Bènard convection, laser arrays, Josephson junctions, CARL...economy ...see for instance S. H. Strogatz, Physica D 143, 1 (2000)

3. Kuramoto model • universal coupling (each to all others) • constant amplitude (implies reservoir) • different resonances (within a small range)

4. Experiment: atoms in a resonator-dipole-trap B. Nagorny et.al., Phys, Rev. A 67, 031401 (R) (2003); D. Kruse et al., Phys. Rev. A 67, 051802 (R) (2003)

5. Elastic scattering from a single localized atom

6. Atom Classical model Cavity

7. bunching parameter:(see also: structure factor, Debey Waller factor) instability: Many atoms: instability and self organization reverse field: source term loss

8. movie1

9. First proof of principle: CARL 1. pump cavity from both sides 2. load atoms into the dipole trap 3. atoms are prebunched 4. block the reverse pumping 5. look at the beat signal 6. observe new frequency atoms D.Kruse et al. PRL 91, 183601 (2003)

10. time domain: frequencydomain: approximate analytic experession numerical simulation experiment Compare experiment and simulation • Interplay between bunching and scattering similar to free electron laser • Collective atomic recoil laser "CARL" (R.Bonifacio)

11. Include damping: viscous CARL 1. pump cavity from a single side2. load atoms into the dipole trap3. activate optical molasses4. look at the beat signal reverse mode starts spontaneously from noise! D.Kruse et al. PRL 91, 183601 (2003)

12. ...and do the simulation Simulation add a friction term...

13. P+(W) threshold due to balance betweenfrictionanddiffusion. Threshold behavior observed ! Theory:G.R.M. Robb, et al. Phys. Rev. A 69,041403 (R) (2004) Experiment: Ch. von Cube et al. Phys. Rev. Lett. 93, 083601 (2004)

14. Focker-Planck Simulation

15. BEC in a Ringresonator

16. Ringresonator L = 85 mm (round trip) nfsr= 3.5 GHz w0 = 107 μm finesse: 87000 (p-polarisation), 6400 (s-polarisation)

17. Einblicke ins Labor

18. BEC in a ringcavity Christoph v. Cube and Sebastian Slama

19. include center of mass motion Rayleigh scattering in the quantum regime only internal degrees

20. atom in a momentum eigenstate: homogeneous distribution: destructive interference in backward direction atom in a superposition state: periodic distribution: constructive interference for light with k=Dk/2 Scattering requires bunching

21. momentum eigenstates optical dipole potential momentum eigenstates scattering more reverse light deeper dipole potential stronger mixing stronger bunching enhanced scattering threshold behavior: decay due to decoherence Rayleigh scattering is a self organization process

22. Superradiant Rayleigh scattering exponential gain for matter waves and optical waves Inouye et al. Science 285, 571 (1999)

23. see also Piovella at al. Opt. Comm. 194, 167 (2001) Two regimes Bad cavity: coherence is stored in the density distribution ! Good cavity: coherence is stored in the light !

24. Simulation of good cavity regime(classical equations)

25. light BEC atoms (time of flight) experiment theory forward power Resonantly enhanced "end fire modes" ofthermal atoms • fully classical model • superradiant peak with several revivals • same qualitative behavior for BEC and thermal cloud

26. good cavity limit (high finesse) - - -: N 4/3..... : N 2 superradiant limit (low finesse) - - -: N 4/3..... : N 2 includes mirror scattering Varying the atom number

27. Future: collective Rabi-oscillations

28. Excursion: Bragg reflection setup for Bragg reflection observed Bragg reflection Bragg beam resonant with 5p-6p transition (421.7nm)waist: 0.25 mm, power: 3µW 3000 Bragg planes with 106 atoms total

29. Reflection angle and lattice constant quadratic increase with atom number as expected for coherent scattering

30. Bragg-interferometer

31. Observing the phase of Rayleigh scattering crucial:Lamb Dicke regimeBragg enhancement

32. CARL team • Sebastian Slama • Gordon Krenz • Simone Bux • Phillipe Courteille • Dietmar Kruse(now Trumpf) • Christoph von Cube (now Zeiss) • Benjamin Deh (now Rb-Li-mixture in Tübingen) • Antje Ludewig (now Amsterdam)

33. Scattering requires bunching scattered power depends on N2 for homogeneous r no scattering 2. This also holds for a single atom no scattering if the atom is in a momentum eigenstate: 3. Scattering requires a superposition state 1. Scattering depends on density distribution

34. Self organization in the quantum picture threshold behavior: decay due to decoherence 1. classical ensemble threshold behavior: diffusion due to heat 2. quantum ensemble (BEC)

35. Results temperatur dependence pump dependence

36. TOF-Aufnahmen

37. Parameter

38. experiment: bimodal distribution RIR-spectrum of a thermal distribution Momentum distribution

39. Christoph von Cube (now Zeiss) • Benjamin Deh (different projekt in Tübingen) • Antje Ludewig (now Amsterdam) • Phillipe Courteille • Sebastian Slama • Gordon Krenz (not on the picture) Visit us in Tübingen !

40. Atoms trapped in the modes of a cavity Running wave mode atoms don‘t hit the mirror !