The scientist who first slowed, and then stopped light will deliver the annual S. Town Stephenson Distinguished Lecture at Washington State University. The talk, “Light at Bicycle Speed…and Slower, Yet!” by Harvard physicist Lene Vestergaard Hau is slated for 7 p.m. Thursday, March 27, in the Webster Physics Building room 16.
In 1999, Hau slowed pulses of light to an incredible 37 miles per hour from its maximum speed of 186,000 miles per second. Later, she completely stopped light for a brief one-thousandth of a second and released it at its full original speed and intensity.
Hau accomplished her feat by sending a beam of light through a tiny drop of Bose-Einstein Condensate, a new state of matter that was predicted by Albert Einstein and Indian physicist Satyendra Nath Bose in 1924. A Bose-Einstein Condensate is created when a collection of atoms are supercooled to a temperature about a billionth of a degree above absolute zero (minus 459.7 degrees Fahrenheit) in an ultra vacuum. At this extremely low temperature the atoms lose their individuality and the blob of atoms behaves as if it were a single particle.
Hau and co-workers discovered that by “massaging” an opaque Bose-Einstein Condensate cloud with laser beams, they could make a light pulse pass through it, but at a slower speed than through any other known substance. After this success, the team stored the light beam briefly within the cloud. To stop the light pulse completely, the massaging lasers were turned off while the compressed light pulse was entirely within the condensate cloud. Although Einstein recognized that light could travel at different speeds through different materials — for example at 140,000 miles per hour through water — he thought storing light would be impossible.
According to Hau, light that is slowed or stopped may find many applications. Her findings could be used in computers that use light instead of electrons to carry and process signals. To this end, she envisions creating tiny light stoppers that will fit on a computer chip. Hau’s research also provides a starting point to simulate black holes for tabletop experiments.
Hau has received a $500,000 MacArthur Fellowship, known as the “genius” award, and published her work in “Nature” magazine. A Dane, she received her bachelor’s, master’s and doctoral degrees in theoretical physics at the University of Carhus and, shortly after, received a Carlsberg Foundation fellowship to study abroad. She joined the Rowland Institute of Science at Harvard in Cambridge, Massachusetts, where she began her studies of the Bose-Einstein Condensate. Today, she is the Gordon McKay Professor of applied physics and professor of physics at Harvard University.
The Stephenson Lecture honors the late S. Town Stephenson, who came to WSU in 1934 and served as chair of the Physical Sciences Division, dean of faculty, and vice president.
Stephenson, who was noted for his research on propagation of radar waves and low-energy x-rays, died in 1964.
The lecture is sponsored by the WSU Department of Physics. A reception follows.