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Double-Entry Laser Light
| Article
# : |
20654 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
10 / 1992 |
2,253 Words |
| Author
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Bruce V. Bigelow
Bruce V. Bigelow is a free-lance science writer in San Diego
and a reporter for the San Diego Union-Tribune. |
It happens in a flash of light, billions of times brighter than sunlight and smaller than a pinpoint.
A pulse of light fired by a high-intensity laser hits a piece of light-sensitive material. In an instant measured in picoseconds (10-12 seconds), a dramatic change occurs within a microscopic spot.
Sometimes, a few thousand molecules hit by the laser pulse respond by emitting their own special light, a reaction called fluorescence. Sometimes, chemical changes occur. Bonds between atoms break or change, and a few thousand molecules reorganize into different compounds, or different versions of the same molecules.
The reactions vary according to complex rules of quantum physics. Yet the particulars are well understood. It is a process known as two-photon excitation.
Today, a handful of scientists are using two-photon excitation in new and creative experiments that are pushing the frontiers of science, offering new opportunities for mind-boggling results.
"The orders of magnitude, the powers of 10 in this problem are just stupendous," says Watt Webb, professor of applied physics at Cornell University.
By using two-photon excitation, Peter Rentzepis, presidential chair and professor of chemistry at the University of California at Irvine, is developing ways to record in 3-D a trillion bits of data within a cubic centimeter--roughly equivalent to storing the contents of a 100,000 book public library in a volume smaller than a sugar cube. Developing such an "optical memory," capable of replacing the magnetic disks in computers, may take 10 years.
A slightly different approach being developed by James Strickler, a graduate student in Webb's lab, could lead more quickly to compact discs capable of storing 30 layers of data--perhaps 10 million pages of text on a single five-inch disc CD-ROM.
By using two-photon excitation, researchers in Webb's group also have obtained unprecedented, precise, three-dimensional pictures of the chemistry within living cells. For example, it is possible to map the concentrations of such key chemicals as soluble calcium throughout the cell.
Webb says it is
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