Non-linear Polarization Rotation in Ultra-Cold Sodium

C. F. Bharucha

Paul D. Lett, P. L. Gould, William D. Phillips +3 more

Justin K. Nash, Frank A. Narducci

In this paper, we report on our first measurements of the linear magneto-optic rotation experienced by a linearly polarized weak probe field as it passes through a sample of cold sodium atoms. The results are compared with theory that does account for the residual Doppler broadening but that does not take into account the recoil experienced by the atoms. We compare the results of our theoretical model with our measurements and find that, at the time of this conference presentation, there still exists a discrepancy. Improvements for future experiments are outlined.

W. Bruce Hawkins, Robert Henry Dicke

Dieter Hils, Wolfgang Jitschin, Hans Kleinpoppen

Sujit Garain, Surya Narayan Sahoo, Ashok Kumar Mohapatra

Non-linear Faraday rotation in cold atoms promises precision magnetometry due to narrower magnetic resonance linewidth compared to the linear Faraday effect. Imaging techniques based on linear Faraday effect have emerged as a tool to characterize the dynamics of ultracold atomic clouds. Using a camera instead of balanced detectors, we can obtain the spatial distribution of polarization rotation in a uniformly intense optical beam. However, the finite dynamic range of the imaging device limits the sensitivity to measure non-linear Faraday rotation at a given incident power. Here, we experimentally demonstrate a differential imaging technique in which we can tune parameters to improve contrast and the sensitivity to the non-linear Faraday rotation signal by a factor of ≈7 over existing imaging methods. The atomic cloud experiences a uniform optical field even when shifted by persistent magnetic fields making the method robust. This allows us to study the effect of transverse fields on non-linear Faraday rotation in ultra-cold atoms, paving the way toward spatially resolved vector magnetometry.