Abstract
We study the optomechanical interaction of a Bose–Einstein condensate with a single longitudinal mode of an ultra-high finesse standing wave optical resonator. As a unique feature the resonator combines three extreme regimes, previously not realized together, i.e., strong cooperative coupling, cavity dominated scattering with a Purcell factor far above unity, and sub-recoil resolution provided by a cavity damping rate smaller than four times the single photon recoil frequency. We present experimental observations in good agreement with a two-mode model predicting highly nonlinear dynamics with signatures as bistability, hysteresis, persistent oscillations, and superradiant back-scattering instabilities.
Highlights
The study of the coupling of single mode radiation to selected electronic degrees of freedom of single atoms has led to the celebrated field of cavity quantum electrodynamics [1, 2] in the eighties and nineties
Examples of such objects are sub-micron mechanical oscillators like cantilevers or membranes or, as in this work, droplets of quantum degenerate atomic gases [5]. When quantum ensembles such as atomic Bose-Einstein condensates (BECs) are considered, a unique arena opens up where the worlds of quantum optics and quantum degenerate many-body physics are brought together in order to prepare and study extreme forms of non-linear quantum matter
We study the most elementary atom-cavity configuration, providing a maximum of control: a BEC interacting with a single longitudinal mode of a standing wave resonator, which is coupled along the cavity axis by a weak external laser beam
Summary
The study of the coupling of single mode radiation to selected electronic degrees of freedom of single atoms has led to the celebrated field of cavity quantum electrodynamics [1, 2] in the eighties and nineties. In the past decade the focus of research has shifted towards the interaction of a single mode of the radiation field with the external degrees of freedom of well controlled macroscopic objects Examples of such objects are sub-micron mechanical oscillators like cantilevers or membranes (which has led to the new field of cavity optomechanics [3, 4]) or, as in this work, droplets of quantum degenerate atomic gases [5]. The regime of resolved recoil results, if the cavity linewidth is smaller than four times the single photon recoil frequency, which corresponds to the kinetic energy transferred to a resting atom by back-scattering of a single photon In this case cavity induced back-scattering can only couple a small number of selected momentum states. The pump beam is detected by a single photon counting module (SPCM), the reference beam is directed to a CCD-camera for monitoring purposes
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