Developments to Watch
VERTICAL LASERS MAY BE READY TO STAND AND DELIVER
Compact-disk players, laser printers, and fiber-optic telephone networks depend on tiny lasers made from semiconductor chips. But such lasers have an expensive quirk: The light they produce shines out of the sides of the chips, and that makes manufacturing them costly. Semiconductor wafers containing hundreds of lasers must first be cut into individual chips. Then each laser--the size of a grain of salt--must be tested and mounted in a product or fiber-optic connector.
To overcome this handicap, Bellcore and other labs have fashioned lasers that shine light upward from the wafer. That way, thousands of lasers can be built, tested, and operated on a single wafer. Groups of such lasers could be used like clusters of transistors on a computer chip. The drawback is that vertical lasers produce only small amounts of light.
Materials engineer Larry A. Coldren of the University of California at Santa Barbara has a better way. By altering the chemical composition and using a diamond layer to conduct excess heat away, Coldren built lasers that run at higher temperatures and produce 10 times more light than previous devices. That kind of power, says Coldren, may enable them to replace traditional "edge" lasers in many products.EDITED BY WILLIAM D. MARBACH