Ultra energy-efficient tungsten bulbs


Researchers at the University of Rochester, led by Chunlei Guo, associate professor of optics, have been experimenting with firing a laser beam through the glass of a tungsten bulb and altering a small area on the filament. When the bulb was lit, they could actually see this one patch was clearly brighter than the rest of the filament although there was no change in the bulb's energy usage.

The key to creating the super-filament is an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse. The laser burst lasts only a few quadrillionths of a second. To get a grasp of that kind of speed, consider that a femtosecond is to a second what a second is to about 32 million years. During its brief burst, the laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to form nanostructures and microstructures that dramatically alter how efficiently can radiate from the filament.

Guo's team has even been able to make a filament radiate partially polarised light, which until now has been impossible to do without special filters that reduce the bulb's efficiency. By creating nanostructures in tight, parallel rows, some light that emits from the filament becomes polarised.

The team is now working to discover what other aspects of a common light bulb they might be able to control. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it to augment regular light bulbs should be relatively simple.

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First Published June 2009

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