Collective Mode Interferences in Light--Matter Interactions

Abstract

We present a theoretical and experimental analysis of transient optical properties of a dense cold atomic gas. After the rapid extinction of a weak coherent driving field (mean photon number ∼ 1.5), a transient 'flash' is observed. Surprisingly the decay of the 'flash' is faster than the decay of the fastest superradiant mode of the system. We show that this 'faster than superradiance decay' is expected due to the interference between collective eigenmodes that exhibit a range of frequency shifts away from the bare atomic transition. Experimental results confirm that the initial decay rate of the superradiant flash increases with optical depth, in agreement with the numerical simulations for the experimental conditions.

Non-exponential decay of a collective excitation in an atomic ensemble coupled to a one-dimensional waveguide

“…We derive the exact dynamics of the collective single excited state in the chiral waveguide, and find that the probability of having an atomic excitation decays with an algebraic power law instead of the conventional exponential decay. This behavior is explained by the coherent interactions, which couple the collective bright state to the many-fold of dark states; similar phenomena have been predicted recently for numerical and approximate approaches in three-dimensions [20]. Remarkably, we demonstrate that this characteristic algebraic behavior remains present even for the bidi-rectional waveguide in the limit of large particle number and extended sample size.…”

“…On one hand, the coupling of the ensemble to an external light field is collectively enhanced which can be used to strongly couple a propagating light pulse to an ensemble of many atoms in order to drive Rabi oscillations with only a few photons [18]. This collective coupling also leads to a strongly enhanced emission rate and the emission becomes highly directional [15,19,20]. On the other hand, coherent interactions mediated by the exchange of virtual photons between the emitters were shown to give rise to a collective Lamb shift [21,22], universal internal dynamics of the ensemble [23] but also strongly influence the decay dynamics of single photon superradiance in three dimensions [17,24,25].…”

Observation of coherent coupling between super- and subradiant states of an ensemble of cold atoms collectively coupled to a single propagating optical mode

“…An ensemble in the timed Dicke state experiences superradiant decay and collectively enhanced emission of light into the same optical mode that excited the system. Likewise, it is possible to introduce N − 1 states, that are orthogonal to the timed Dicke state and subradiant with respect to the optical mode with wavevector k. This approach is suitable for describing a considerable number of physical systems, including for instance cold atom clouds [3][4][5][6][7][8][9][10], Rydberg atoms [11,12] and emitters in solid state samples [13]. In addition, in cavity quantum electrodynamics the timed Dicke physics is at the basis of the assumptions of the Tavis-Cummings model [14,15], which describes collectively enhanced light-matter coupling between an atomic ensemble and a single mode cavity [16,17].…”

“…where χ N (t) is the complex amplitude of the light field right after the N th atom and v g is the group velocity of the guided optical mode. We note that Γ ens (t) is sometimes inferred from the decay rate of the light intensity emitted by the atoms into the considered mode, Γ light (t), [4,5,9,10,12], i.e. :…”

Optical Magnetism and Huygens' Surfaces in Arrays of Atoms Induced by Cooperative Responses

“…Moreover, the atomic arrays can offer a promising platform for quantum information processing at the level of single photon excitations [24,40,41]. Experiments on strong collective optical responses of trapped cold atomic ensembles are actively ongoing [42][43][44][45][46][47][48][49][50][51][52][53][54], and the first measure-ments of the transmitted light through an optical lattice of atoms in a Mott-insulator state have now been performed [55] that demonstrate subradiant resonance narrowing where the entire lattice responds as a coherent collective entity.…”