Group Seminar via Zoom: Raman Imaging of Small Atomic Ensembles Inside an Optical Cavity

September 29, 2020

Maximilian Ammenwerth, IAP Bonn
Group meeting via video conference (Zoom)
Tuesday, September 29th, 9:00 (MEZ)

Dealing with the unique situation of partial lock downs worldwide and home office solutions at our Institute due to the current spreading of the Covid 19 virus, we are now holding our group seminars and journal clubs via video conference. This procedure enables us to continue our research, enhance discussions and exchange important information.


I present fluorescence imaging of 87Rb atoms inside an optical cavity using the Raman imaging technique, that is based on detecting the repumper fluorescence during Raman sideband cooling. The first part describes precision measurements of the differential light shifts that occur during continuous Raman sideband cooling. These light shifts are caused by the optical repumper beam and modify the two-photon resonance of the Raman coupling. The cooling process is modeled by means of a three-level system that takes into account the Raman coupling and the repumping process. We find good agreement between the estimated and the measured light shifts. In addition, we observe that it is beneficial to detune the optical repumping beam away from resonance in order to suppress detrimental heating due to dipole force fluctuations [1]. The characterization of differential light shifts is used to optimize the fluorescence imaging of atoms inside the resonator. The complexity of the parameter space is reduced via a two-photon feed-forward which maintains the resonance with the Raman cooling sideband when varying the repumper parameters. Using a cavity-based atom detection, we independently measure the probability that a single atom survives the exposure time of 1s and optimize the fluorescence detected with an EMCCD camera. Raman imaging is successfully applied to image small atomic ensembles inside the resonator. This constitutes the first step towards photon storage experiments with multiple atoms in our experiment.

[1] M. Martinez-Dorantes et al., PRA 97 023410 (2018)

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