Photonics Center Improves Semiconductor Lasers
Scientists working in the UW-Madison Reed Center for Photonics have made technological breakthroughs in semiconductor lasers that promise to radically reduce the costs and improve the reliability of fiber-optic networks.
"We're able to get twice the coherent power that had previously been achieved and potentially we'll be able to get five times the coherent power of existing semiconductor lasers," says Dan Botez, Philip D. Reed professor of electrical and computer engineering. Botez's team in the Photonics Center has developed a new process for producing high-power, aluminum-free diode lasers in the 0.78 to 0.98 micron range. Aluminum-free lasers have the potential to be more reliable, more powerful and more efficient than common aluminum-gallium-arsenide diode lasers. The group has made aluminum-free lasers that provide three watts of continuous-wave power, a record.
One application for these lasers is as signal boosters, or "pumps," in telecommunications networks. Current pump lasers must be placed at least every 20 miles. Botez's more powerful lasers would allow the light pumps to be spaced at 45-mile intervals, reducing the networks' cost significantly. These lasers are also critical to such applications as medical imaging, optical data recording systems and free-space communication for satellites and aircraft.
Aluminum-free lasers should be more reliable because they are freer of contaminants and because their lower electrical resistance makes them less likely to overheat. "During manufacturing, contaminants result from aluminum oxidizing." Botez explains. And, he says, "the aluminum-free devices' electro-optical characteristics are virtually temperature insensitive." It is this insensitivity to temperature that both allows the lasers to be made in higher-power models and makes them more efficient.
This work is described in the February 15 issue of Electronics Letters and has been accepted for presentation at the IEEE/OSA CLEO '96 conference, which will be held June 2 through 7 in Anaheim, California.