Trapping and Stopping/Cooling of Atoms, Particles, and Bio-components Using Laser Light

Galina A. Nemova

Richard N. Watts, Carl Wieman

The use of light presure to cool and stop neutral atoms has been an area of considerable interest recently. Cooled neutral atoms are needed for a variety of interesting experiments involving neutral atom traps and ultrahigh-resolution spectroscopy. Laser cooling of sodium has previously been demonstrated using elegant but quite elaborate apparatus.1,2 These techniques employed stabilized dye lasers and a variety of additional sophisticated hardware. We have demonstrated that the frequency chirp technique of Ref. 2 can be implemented using inexpensive diode lasers and simple electronics.

Carl Wieman

There has been considerable activity recently on cooling and trapping atoms using laser light. This work raises expectations that laser manipulation of atoms will be an important new tool for atomic physics. However, up to now, almost all the work has been on sodium atoms using light from dye lasers. The expense and complication of a narrowband dye laser system is a considerable limitation on the possible uses of this tool. In response to this we have been exploring the use of inexpensive diode lasers for the manipulation of atoms. We have found that diode lasers work very well for this purpose and even have some advantages over dye lasers in addition to cost and ease of use. We previously reported using light from diode lasers to stop a beam of atomic cesium. Here we discuss our more recent work using diode lasers to produce extremely cold cesium vapor via optical molasses cooling and the demonstration of a new type of optical trap. This is a purely optical spontaneous force trap which uses spatially inhomogeneous optical pumping to circumvent the optical Earnshaw theorem.

Steven Chu, John E. Bjorkholm, Arthur Ashkin +2 more

Vanderlei Salvador Bagnato, Gregory P. Lafyatis, Alexander G. Martin +2 more

We have continuously stopped thermal sodium atoms with laser light and loaded them into a 0.1-K deep superconducting magnetic trap. The trap is formed by a local minimum of the magnetic field produced by two superconducting coils and a radially confining octupole field. The atoms are slowed and stopped in two stages: The atoms are first slowed to ~200 m/s using a counterpropagating resonant laser beam and tapered magnetic field to compensate for the changing Doppler shift as the atoms are slowed.1 A second laser beam and tapered magnetic field, actually located within the trap, are used to stop the atoms in the trap. This continuous loading process has allowed us to accumulate up to 1 × 109 trapped atoms, and trapping times of several minutes have been achieved. Our trap has the feature of having a uniform magnetic field at its bottom, opening up the possibility of precision spectroscopy of the trapped atoms. The fluorescence from the trapped atoms has been studied, and they have been cooled to ~1 mK using 1-D optical molasses.

Philip H. Jones, Onofrio M. Maragò, Giovanni Volpe