Biochromatic Force

See also Publications on this topic, also listed below

        In the early days of laser cooling, the view of two-level atoms moving in a monochromatic laser beam provided a sufficient picture. The topics that could be described this way included atomic beam slowing and cooling, optical molasses, optical dipole traps, lattices and band structure effects, and a host of others. Within a few years, however, it became clear that this simple two-level atom view was inadequate, and that the multiple level structure of atoms was necessary to explain some of the experiments. This opened the way for a new era in laser cooling by providing descriptions of sub-Doppler cooling, magneto-optical trapping, velocity selective coherent population trapping, and many others. One might expect a similar plethora of new phenomena to emerge from the use of multiple beams of light of different frequencies or changing frequencies, (i.e., non-monochromatic) light, but this topic has been largely ignored.

        The bichromatic force derives from improved control of the momentum exchange between the atoms and the light field. The forces arise by implementing a carefully orchestrated, rapid, coherent sequence of absorptions followed by stimulated emissions using non-monochromatic light, while comparatively infrequent spontaneous emission provide the irreversible processes required for the phase space compression that constitutes cooling. This force is both very much stronger and spans a very much larger velocity range than the ordinary radiative force that has been used for laser cooling since the early 1980's. Since it covers such a large range of velocities, Doppler compensation is not necessary for slowing a thermal beam. It also has a strong velocity dependence at its range boundaries, so that it can cool.

Publications:

"Measurement of the Bichromatic Optical Force On Rb Atoms", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Accepted for publication in Phys. Rev. A, Rapid Comm. Sept. 1999.

"A Dressed Atom View of Bichromatic Forces", (H. Metcalf), in preparation.

"Study of the Bichromatic Force by Atomic Beam Deflections", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Submitted to Phys. Rev. A, July 1999.

Abstracts

"Dressed State Description of Bichromatic Forces", (H. Metcalf), Bull. Am. Phys. Soc. 43 (1998).

"Measurement of the Bichromatic Force in 1-D", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Bull. Am. Phys. Soc. 43 (1998).

"Proposal for an Atomic Prism/Collimator", (M. Williams, M. Cashen, and H. Metcalf), Bull. Am. Phys. Soc. 43 (1998).

"The Stimulated Bichromatic Force", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Abstracts of ICAP XVI, Windsor, 1998, 448, (H26).

"Precise Measurement of the Bichromatic Force", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Bull. Am. Phys. Soc. 44, 725 (1998), NP01-24.

"Precise Measurement of the Bichromatic Force", (M. Williams, F. Chi, M. Cashen, and H. Metcalf), Conference on Atom Optics Applications, Les Houches, Fr., May 1999.