Electromagnetically Induced Collisional Transparency


Eduardo Gomez, Lincoln Turner, Adam Black,

Michael Johanning, Paul Lett, and William D. Phillips


National Institute of Standards & Technology, Atomic Physics Division

 100 Bureau Drive, Stop 8424, Gaithersburg, MD 20899-8424, USA



We study the collision of two moving sodium Bose-Einstein condensates in the presence of light that couples pairs of atoms in the electronic ground state to electronically excited molecules. This photoassociation process greatly enhances atom-atom collisions, rendering one cloud “opaque” to the other. In this poster, we describe the addition of a second, “control” laser coupling the excited molecules to ground molecular states. This forms an atom-molecule coherence that is uncoupled to the excited state molecules, and constitutes a collisional dark state. For appropriate laser frequencies, the atom-atom collisions are suppressed so that the clouds pass through one another with little perturbation.

Electromagnetically induced transparency (EIT) is conventionally an optical effect that coherently couples the internal levels of individual atoms. A strong control laser evolves the system into a dark state that is transparent to a probe laser. This transparency window is spectrally narrow and exhibits extreme dispersion, leading to phenomena such as superluminal or meters-per-second group velocities.

            Similarly, in the collisional EIT experiment, we expect to observe an analogous window of transparency in the relative velocity of the two condensates. This would indicate that the control laser has produced a coherent superposition of free atoms with ground-state molecules. Such coherence would give rise to the possibility of observing dispersion in the propagation of matter waves analogous to that which is evident for light in conventional EIT.


Names:                        Eduardo Gomez, Lincoln Turner, Adam Black

Mentor's name:            Paul Lett

Division:                      Atomic Physics Division (842)

Laboratory:                  Laser Cooling and Trapping Group

Address:                       Rm. E110, Bldg. 216, Stop 8424

Telephone #:                (301) 975-2353

FAX #:                        (301) 975-8272

email:                           adam.black@nist.gov