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NEW Blue Laser MAY REVOLUTIONIZE VIDEO SCREENS, OPTICAL STORAGE Novel Fabrication Technique is the Key
(Boston, Mass.) -- Scientists at Boston University have announced the development of a new blue laser that may lead to a new generation of more vivid color video screens and computer displays as well as optical storage disks that can hold four times the amount of information that can be squeezed onto today's new digital video disks.
In a paper that appears this month in Issue 4 of Electronic Letters, Dr. E. Fred Schubert, professor of electrical and computer engineering and a member of the faculty of the Photonics Center at Boston University, reports the fabrication of the world's first gallium nitride (InGaN) double-heterostructure laser, which emits blue light. Scientists around the world have been searching for efficient ways to make lasers that emit these shorter wavelengths because they will open the door to a host of new applications.
Ease of fabrication is the key to commercial success, and it is the fabrication technique that has caused a stir in the scientific community. Along with Dean Stocker, a doctoral candidate in physics, Schubert fashioned the laser from extremely small pieces of polished sapphire under even smaller layers of semiconducting crystal. The laser materials were then scored with a diamond and then "cleaved"--or broken--along the scratch to produce extremely smooth facets that control the paths of the photons that make up the laser beam.
The smoothness of the cleaved surfaces is a critical determinant of the performance of the device, and the scientists measured the surface roughness to be well within the required limits--just 20 billionths of a meter, or 1/4,000 the thickness of a human hair.
"The ability of these materials to cleave was not established previously," says Schubert. "We've demonstrated not only that the sapphire cleaves well, but that the active material on the sapphire, the GaN, produces an incredibly smooth surface. This is a very manufacturable technique."
The resulting device is extremely efficient: doubling the input current can boost the light output as much as 200-fold.
Schubert and Stocker have been working with Advanced Technology Materials, Inc., a Connecticut-based company which furnished materials for the project. The scientists first presented their work in poster format at a meeting of the Materials Research Society in early December, 1997 where it generated considerable interest. They anticipate approval of a patent application for their invention within the next six months.
Before joining the faculty of the Photonics Center and the College of Engineering at Boston University, Schubert was a member of the technical staff of AT&T Bell Laboratories in Murray Hill, New Jersey (now known as Lucent Technologies). He holds more than 20 U.S. patents and 40 foreign patents for the development of optoelectronic and electronic devices and semiconductor materials.
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February 12, 1998
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