Will Light Bulbs Go The Way Of The Victrola?
The lightbulb has been humanity's most reliable source of artificial illumination since Thomas A. Edison perfected the design in 1878. That may be about to change. Just as the vacuum tube was replaced by integrated circuitry in the late 1950s, the lightbulb may soon be threatened by a new generation of solid-state light-emitting electronics that could send Edison's venerable invention the way of the Victrola.
Light-emitting diodes (LEDs) that glow red are already replacing the bulbs in traffic lights and automobile taillights (table). LEDs and some semiconductor lasers can also emit blue, green, and yellow light, spurring research efforts in new types of flat-panel displays. But until recently, no one had found a practical way to coax a solid-state device into producing the familiar white light that illuminates homes and workplaces. The answer may be arrays of tiny lasers developed jointly by researchers at Brown University in Providence, R.I., and Sandia National Laboratories in Albuquerque, N.M.
The scientists discovered a way to create a class of microlasers known as VCSELs, for vertical-cavity surface-emitting lasers, that produce ultraviolet radiation. It is ultraviolet light that causes the phosphors on the inside of gas-filled fluorescent lights to glow white. The researchers believe that these same phosphorescent coatings could turn arrays of tiny lasers into practical lamps. "Many groups are racing to create such lasers in the UV range," says Jung Han, who heads the Sandia group. "It was a dream. Now, we have achieved it."
The market potential for such solid-state lights could be enormous. Around $15 billion worth of conventional lamps are sold each year worldwide. And by most measures, solid-state lights will be superior. They will last up to 10 times longer than fluorescent tubes and will be far less fragile. They also promise to change the way spaces are lit. Flat arrays can be mounted in any pattern, on floors, walls, ceilings, or even furniture.
The biggest payoff, however, is likely to be in saved energy. Last year, researchers at Sandia and Hewlett-Packard Co. predicted that solid-state lighting applications would chop energy costs by $100 billion annually by 2025. Demand for electricity would be reduced by 120 gigawatts per year--the equivalent of about 15% of current U.S. generating capacity. Another plus: carbon-emission reductions of 350 million tons a year. "No other major electricity application represents such a large energy-savings potential," they concluded in a presentation at a meeting of the Optoelectronics Industry Development Assn. (OIDA).
The Brown and Sandia researchers believe VCSELs have the brightest future because they create a monochromatic and directional beam. But other approaches are vying for the huge lighting market. Blue LEDs, for example, can be combined with phosphors to create white light, a solution that some developers prefer because blue LEDs are already in production. In the U.S., GelCore Corp. in Valley View, Ohio, a joint-venture between GE Lighting and Emcore Corp., and Cree Lighting Inc. in Goleta, Calif., are exploring this approach. Such light is harsh and cold, however, because it is overweighted toward the blue spectrum, according to the Sandia team. White light also can be produced by arrays that combine the spectral ranges of red, blue, and green LEDs, but they are difficult and costly to fabricate.
BIG HURDLE. Sandia also has a long way to go before a practical lamp emerges. The next challenge: standardizing the technology so it can be incorporated into existing lighting and electrical fixtures. Even if researchers can lick this problem, "it's probably in the 5- to 10-year time frame" before VCSELs are commercialized, says Robert M. Biefeld, a Sandia scientist.
The white-lighting developers hope to pick up the pace--with a little help from the government. Last fall, the Energy Dept. and OIDA brought together key researchers at a joint conference in Albuquerque. Their mission was to agree on a "roadmap" for accelerated development of solid-state illumination for civilian and military applications.
That report, they hope, will lead to national initiatives of the sort that are already in place in Japan, Taiwan, South Korea, and Europe. The goal is to secure the U.S. a competitive position in a vast new market. "We are looking at a new paradigm in lighting that has enormous economic implications," says Arpad A. Bergh, president of OIDA.
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