The light that emerged from the apparatus, not visible to the naked eye, was only 25 percent as strong as the light that entered, but detectors found that it had roughly the same color. The speed of light is reduced in any transparent medium, including water, plastic and diamond. Glass prisms and lenses, for example, slow light by differing amounts that depend on the thickness of the glass. The slowing of light causes the bending by which lenses focus images. Not only is the speed brought to a crawl, but the refractive index of the condensate becomes gigantic.
Refractive index is a measure of the degree to which a medium bends light.
The refractive index of the condensate created by Dr. Hau's group was about 100 trillion times greater than that of a glass optical fiber. Possible applications include ultrasensitive night-vision glasses and laser light projectors that could create very bright projected images. Laser-condensate combinations may also lead to ultrafast optical switching systems useful in computers that would operate using one light beam to control another light beam. Such a system could function as an optically switched logic gate, replacing the electronic logic gates computers now use. Slow light could also be exploited in filtering noise from optical communications systems, Dr. Hau said.