Description
We experimentally and theoretically investigate collective effects in a one-dimensional array of cold atoms coupled to a single-mode optical nanofiber [1]. Our analysis unveils the microscopic (i.e., atom per atom) dynamics of the system, showing that collective interactions gradually build-up along the atomic chain in the direction of propagation of the excitation light pulses. Our theoretical results are supported by time-resolved measurements of the light transmitted and reflected by the atomic ensemble.
In particular, when the excitation pulse is switched off on a time scale much shorter than the atomic lifetime, a superradiant decay is observed in the forward direction, while no speed-up of the decay rate is measured in the backward direction. For longer time scales, our measurements reveal the evolution of the ensemble from the superradiant state to a set of states that are fully subradiant with respect to the fiber mode [2]. Notably, our theoretical model identifies this phenomenon as a key feature of the time evolution of one-dimensional systems prepared in a timed Dicke state. This complex dynamics can be accurately described with a simple analytical expression.
Our results highlight the unique opportunities offered by nanophotonic cold atom systems for the experimental investigation of collective light-matter interaction.
[1] R. Pennetta et al., “Collective Radiative Dynamics of an Ensemble of Cold Atoms Coupled to an Optical Waveguide”, Phys. Rev. Lett., 128, 073601 (2022)
[2] R. Pennetta et al., “Observation of coherent coupling between super- and subradiant states of an ensemble of cold atoms collectively coupled to a single propagating optical mode”, Phys. Rev. Lett. (accepted)
| Presenter name | Riccardo Pennetta |
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