**8. Demonstration of a cloud of cold atoms**

After controlling and locking the laser frequencies and finding the necessary magnetic field strength it was possible to observe a cloud of atom that was visible with the surveillance camera. Simultaneously we observed the cloud with our second CCD camera. The correct magnetic field direction was found by trial and error. For this we changed the polarity on the magnetic field power supplies while adjusting the best laser frequencies. Fig.26 shows a typical image obtained with our surveillance camera in our initial setup.

Fig. 26. Cloud of atoms obtained with surveillance camera. Left: no cloud, right: cloud of cold atoms.

Fig. 27 shows image taken with a modified Samsung photo camera. In this case we removed the optics from the camera and the IR filter. We placed a 50 mm camera lens in front of the camera.

178 Quantum Optics and Laser Experiments

error signal (a.u.)

Fig. 25. Experimental error function.

**8. Demonstration of a cloud of cold atoms** 

interferometer.

cold atoms.


To lock the laser frequency to the needed resonance, we have stored one single Doppler free spectrum and recalled and displayed it on the oscilloscope screen. The amplitude scan was decreased close to the zero crossing of the error function. Adjustments of the error signal position relative to the Doppler free spectra could be done by changing the absolute cavity length of the interferometer. This was done by changing the offset bias voltage of the

After controlling and locking the laser frequencies and finding the necessary magnetic field strength it was possible to observe a cloud of atom that was visible with the surveillance camera. Simultaneously we observed the cloud with our second CCD camera. The correct magnetic field direction was found by trial and error. For this we changed the polarity on the magnetic field power supplies while adjusting the best laser frequencies. Fig.26 shows a

Fig. 26. Cloud of atoms obtained with surveillance camera. Left: no cloud, right: cloud of

Fig. 27 shows image taken with a modified Samsung photo camera. In this case we removed the optics from the camera and the IR filter. We placed a 50 mm camera lens in front of the camera.

typical image obtained with our surveillance camera in our initial setup.

Fig. 27. Image taken with modified Samsung camera. The chamber can be seen.

Fig. 28 shows the cloud image obtained with the IR Altec Vision CCD camera. The cloud diameter was nearly 2.0 mm at its full width.

Fig. 28. Cloud of atoms obtained with our Altec Vision IR CCD camera. Left is the cloud image and right a 3D plot of intensity of the same cloud.
