INVESTIGATION OF ATOM IMAGING BY ELECTRIC FIELD

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Focusing lenses are indispensable components of atom optics. Popular methods of realizing convex lenses are diffraction by near resonant laser light and by micro-fabricated transparent interferometric structures. We use electric field to realize a convex lens. The Stark effect of atoms in a stable state is negative. Therefore, atoms are pulled towards the local maximum of electric field intensity. Though it is not possible to generate a local maximum of static electric field in free space, microwave field can. We use a cylindrical microwave cavity in TM010 mode to focus a slow neon atomic beam that is generated from a trap of metastable neon atoms. The radial variation of the electric field of the TM010 mode is the 0th order Bessel function and has a maximum on axis. The diameter of the cavity is inversely proportional to the frequency. However, the focusing power increases proportional to the cube of the frequenct. Therefore, it is advantageous to use the highest frequency that can transmit entire atomic beam through the cavity. We use 17GHz microwave. The diameter and the length of the cavity are 13mm and 13 cm, respectively. The Q value of the cavity was approximately 6000. The slow atoms are vertically dropped. The pattern of the atomic beam below the cavity is detected by a micro-channel detector that can produce two-dimensional image with the resolution of approximately 50 micron meters. A clear focusing was observed at the distance 60cm below the cavity with the microwave power of 13.5W.