Spatial density measurement of trapped atoms

Spatial density measurement for Magnet Optic trap is quite easy, because the magnet optic trapped atoms are always radiating spontaneous emitted photons. However, it is not so easy to measure the spatial density of no photon radiating atoms, such as magnetic trapped atoms.

The useful technique for such atoms are
1) inject near resonant projection pulse and image the absorption profile,
2) inject far off-resonant pulse and image the phase contrast.
When measuring relatively low density atoms, the 1st technique is easier than the 2nd one. I use the 1st technique in my laboratory and measure the temperature, density, and, etc of atoms in both MOT and MT.

Fig. 1 is the experimental setup of this absorption imaging technique. The projection pulse duration is 10 micro-second, and the peak intensity is about 60% of the transition saturation, i.e. about 9 photons per atom for a measurement are absorbed and about 100 micro-kelvin heat up is introduced for a measurement. For this reason this is a demolision measurement.

Fig.1 : Experimental set-up for the absorption imaging. (35KB GIF)

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