LIGHT AT 1 MPH. A year ago Lene Verstergaard Hau used a Bose Einstein condensate (BEC) as a special nonlinear optical medium for slowing light from 3 x 10⁸ m/sec to a mere 17 m/sec (38 mph; Update 415). This comes about when an incoming light pulse enters the BEC and experiences an extremely abrupt change in index of refraction (and as for absorption of the light, this is prevented by applying two laser beams which induce a transparency at the frequency of the incoming light).

In a talk presented at this week's meeting of the American Association for the Advancement of Science (AAAS) in Washington, DC, Hau said that she and her Harvard colleagues had slowed the light further, to a speed of 1 mph. She said that if the velocity could be slowed still more, to a value of 1 cm/sec, then this would be comparable to the speed of sound in the condensate and it might be possible to get atoms to surf on the front of the light pulse. Hau believes that this approach to slowing light, if it can be simplified, would lead to highly sensitive light switches and to low-power nonlinear optics (right now high-power laser light is required to produce nonlinear effects).