U.S. scientists have used an ultra-powerful laser to turn regular incandescent light bulbs into super-efficient sources of light.

University of Rochester (N.Y.) researchers said the laser creates a unique array of nano- and micro-scale structures on the surface of a regular tungsten filament. It's those structures that make the tungsten emit light as bright as a 100-watt bulb, but consume less electricity than a 60-watt bulb.

"We've been experimenting with the way ultra-fast lasers change metals, and we wondered what would happen if we trained the laser on a filament," Associate Professor Chunlei Guo said. "We fired the laser beam right through the glass of the bulb and altered a small area on the filament. When we lit the bulb, we could actually see this one patch was clearly brighter than the rest of the filament, but there was no change in the bulb's energy usage."

The key to creating the super-filament is an ultra-intense beam of light called a femtosecond laser pulse. The researchers said the laser burst lasts only a few quadrillionths of a second, but it unleashes as much power as the entire electricity grid of North America onto a spot the size of a needle point.

The findings are to appear in an upcoming issue of the journal Physical Review Letters.