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

2. 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) applause synchronization A.-L. Barabási, Nature 403, 849 (2000) milleniums bridge Strogatz, et. al, Nature, 438, 43-44 (2005) glow worms chirping crickets

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. Classical model Atom Cavity

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

8. movie1

9. First proof of principle: CARL atoms D.Kruse et al. PRL 91, 183601 (2003) 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

10. Compare experiment and simulation time domain: frequency domain: numerical simulation approximate analytic experession experiment 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 side 2. load atoms into the dipole trap 3. activate optical molasses 4. look at the beat signal reverse mode starts spontaneously from noise! D.Kruse et al. PRL 91, 183601 (2003)

12. Simulation...and do the simulationadd a friction term...

13. 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) threshold due to balance between friction and diffusion. P + (W)

14. Focker-Planck Simulation

15. BEC in a Ringresonator

16. Ringresonator L = 85 mm (round trip) fsr = 3.5 GHz w 0 = 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. Rayleigh scattering in the quantum regime only internal degrees include center of mass motion

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

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

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

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

24. Simulation of good cavity regime (classical equations)

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

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

27. Future: collective Rabi-oscillations

28. Excursion: Bragg reflection setup for Bragg reflectionobserved Bragg reflection Bragg beam resonant with 5p-6p transition (421.7nm) waist: 0.25 mm, power: 3µW 3000 Bragg planes with 10 6 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 regime Bragg 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 1. Scattering depends on density distribution for homogeneous  no scattering scattered power depends on N 2 2. This also holds for a single atom no scattering if the atom is in a momentum eigenstate: 3. Scattering requires a superposition state

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

35. Results temperatur dependencepump dependence

36. TOF-Aufnahmen

37. Parameter

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

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

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