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Abstract

We have demonstrated that a suitably magnetized surface can be used to retroreflect cold atoms for applications in atom optics. This has some advantages relative to evanescent wave mirrors because no light is involved. Multiple bounces of cold rubidium atoms have been observed for times up to 1 s in a trap formed by gravity and a 2 cm diameter spherical mirror made from a flexible computer disk ('floppy disk'). We have studied the dynamics of the atoms bouncing in this trap from several different heights up to 40.5 mm and we conclude that the atoms are reflected specularly and with reflectivity 1.01(3). The performance of this mirror is limited at present by collisions with the background gas and by unwanted harmonics in the magnetization of the surface. This is the first in a series of papers concerning the use of magnetized surfaces in atom optics.

Reconstruction of a Cold Atom Cloud by Magnetic Focusing

“…We have also studied the behavior of clouds released from R͞2, the analog in photon optics of placing the light source at the center of curvature. We see as predicted [14] that the original atom cloud is now reconstituted at the peak of the first bounce and that the focusing is again independent of temperature.…”

“…Subsequently we made a floppy disk mirror whose surface was covered completely by positioning the record head to write overlapping tracks. This produced a smoother reflector but still diffused the atoms by 648 mrad [14], making it impossible to observe any focusing of the cloud. This roughness was due to second and third harmonics in the magnetization and to the discontinuities between one track and the next [15].…”

“…A magneto-optical trap [5] collects approximately 5 3 10 6 atoms of 85 Rb in a 1 mm cloud situated 13.5 mm above the reflector. The height R͞4 is the focal plane of the mirror, a factor of 2 different from ordinary optics because the atoms fall under gravity on parabolic trajectories [14]. After being released from the trap, the atoms are cooled by optical molasses [5] for 20 ms, then optically pumped for 1 ms by a retroreflected s 1 light beam, which transfers the majority of them to the most favorable state for magnetic reflection ͑F 3, M F 13͒.…”

Cold atoms in videotape micro-traps

“…These include audiotape [1], floppy disks [2,3,4], videotape [5,6], magneto-optical films [7,8,9], and hard disks [10]. Using standard lithographic techniques, it is also possible to make small patterns of current carrying wires for the same purpose [11,12].…”

Magnetic Waveguide for Trapping Cold Atom Gases in Two Dimensions

“…At a distance z above the surface, the magnitude of the field is B max exp͑22p z͞l͒ [16]. Such surfaces have been developed recently for reflecting and focusing slow atomic beams through the Zeeman interaction, which is able to retroreflect atoms dropped from heights of many centimeters [17][18][19][20][21]. Here, we show how the Zeeman shift in sublevel F 3, m F 22, labeled f in Fig.…”