Ultraslow Light Pulse Propagation Observed in Atoms—Both Cold and Hot

Earlier this year, Lene Hau (Rowland Institute for Science and Harvard University) and her coworkers captured the media spotlight with their announcement of having slowed the speed of light pulses through a Bose—Einstein condensate to a mere 17 m/s, down by a factor of nearly 20 million from light’s speed in vacuum. (See Physics Today, April 1999, page 9.) Marian Scully and his colleagues at Texas A&M University, the National Institute for Standards and Technology in Boulder, Colorado, and the Harvard‐Smithsonian Center for Astrophysics have recently reported comparable results using an ensemble of rubidium atoms that, at a temperature of 360 K, are a billion times hotter than Hau’s sodium atoms. And Dmitry Budker’s group at the University of California, Berkeley has seen even slower speeds in rubidium at room temperature. Accompanying the slow speeds are extremely nonlinear optical properties, as well.

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