Laser driven superradiant ensembles of two-level atoms near Dicke's regime

Abstract

We report the experimental observation of superradiant emission emanating from an elongated dense ensemble of laser cooled two-level atoms, with a radial extent smaller than the transition wavelength. In the presence of a strong driving laser, we observe that the system is superradiant along its symmmetry axis. This occurs even though the driving laser is orthogonal to the superradiance direction. This superradiance modifies the spontaneous emission, and, resultantly, the Rabi oscillations. We also investigate Dicke superradiance in the emission of an almost fully-inverted system as a function of atom numnber. The experimental results are in qualitative agreement with ab-initio, beyond-mean-field calculations.

Theoretical study of early-time superradiance for atom clouds and arrays

“…As we will see below and was experimentally observed in Ref. [27], there are cases where γ(0, k) > 0 for some directions k even though γ(0) < 0. However, for γ(0, k) > 0, there must be nonzero (and substantial) pair correlations developing in the atom cloud even when γ(0) < 0.…”

“…As an example, Ref. [27] experimentally demonstrated cases with clear superradiance in a particular direction (as evidenced by increasing photon emission rate at early time) with no enhancement in other directions and Ref. [64] theoretically investigated directional superradiance for weakly illuminated atom arrays.…”

Theoretical study of early time superradiance for atom clouds and arrays

“…As an example, Ref. [27] experimentally demonstrated cases with clear superradiance in a particular direction (as evidenced by increasing photon emission rate at early time) with no enhancement in other directions. While the theory can be used for randomly placed atoms, all examples below are for atom arrays.…”

Dicke superradiance in ordered lattices: dimensionality matters

“…1(a)]. This "superradiant burst" has become a hallmark of collective phenomena in quantum optics and has been observed in a variety of physical systems [5][6][7][8][9][10][11]. Generally, experiments are performed in dense disordered systems, where interparticle separations can be very small, or in a cavity, where the restriction of the field to a single confined mode emulates the condition of atoms at a point.…”