Cavity-enhanced superradiant Rayleigh scattering with ultracold and Bose-Einstein condensed atoms

Abstract

We report on the observation of collective atomic recoil lasing and superradiant Rayleigh scattering with ultracold and Bose-Einstein condensed atoms in an optical ring cavity. Both phenomena are based on instabilities evoked by the collective interaction of light with cold atomic gases. This publication clarifies the link between the two effects. The observation of superradiant behavior with thermal clouds as hot as several tens of µK proves that the phenomena are driven by the cooperative dynamics of the atoms, which is strongly enhanced by the presence of the ring cavity.

Steady-state, cavityless, multimode superradiance in a cold vapor

“…Multi-mode superradiance has been observed in such systems [8], although the emission is inherently transient because the recoil associated with repeated scattering events eventually destroys the ultracold gas. Alternatively, placing the atoms in a singlemode cavity effectively increases the coherence time of the system and enables superradiance to occur at temperatures of up to hundreds of µK [5]. Unfortunately, single-mode cavities are incompatible with multi-mode fields, which are necessary for realizing recently-proposed spin glass systems [7,10,13] and multi-mode quantum information processing schemes [14,15].…”

“…In these studies, an initially uniformly-distributed gas of atoms pumped by external optical fields spontaneously undergoes a transition to a spatially-ordered state under certain circumstances [5][6][7][8]. This ordering arises from the momentum imparted to the atoms via optical scattering and can be understood as a form of atomic synchronization: instead of the atoms scattering light individually, the self-assembled density grating enables the entire ensemble to coherently scatter light as a single entity.…”

“…One prominent example of collective behavior is superradiance [3], where light-induced couplings between initially incoherentlyprepared emitters cause the full ensemble to synchronize and radiate coherently [4]. While early studies of superradiance focused on collective scattering via the emitters' internal degrees of freedom, recent work demonstrates that formally identical behavior arises through the manipulation of the center-of-mass positions and momenta of cold atoms [5][6][7].…”

“…The main dephasing mechanisms are grating washout due to thermal atomic motion and the loss of photons from the interaction volume [5]. One can overcome the effects of thermal motion in free space by working at ultracold temperatures (T < 3 µK) and using optical fields detuned far from the atomic resonance in order to avoid recoilinduced heating [8,12].…”

“…One prominent example of collective behavior is superradiance [3], where light-induced couplings between initially incoherentlyprepared emitters cause the full ensemble to synchronize and radiate coherently [4]. While early studies of superradiance focused on collective scattering via the emitters' internal degrees of freedom, recent work demonstrates that formally identical behavior arises through the manipulation of the center-of-mass positions and momenta of cold atoms [5][6][7].In these studies, an initially uniformly-distributed gas of atoms pumped by external optical fields spontaneously undergoes a transition to a spatially-ordered state under certain circumstances [5][6][7][8]. This ordering arises from the momentum imparted to the atoms via optical scattering and can be understood as a form of atomic synchronization: instead of the atoms scattering light individually, the self-assembled density grating enables the entire ensemble to coherently scatter light as a single entity.…”