Thanks to a bit of ingenuity, Chunlei Guo, associate professor of optics at the University of Rochester, and his assistant Anatoliy Vorobyev have been able to squeeze out fluorescent-like energy performance from an incandescent light bulb. The breakthrough boils down to a laser treatment of the bulb's tungsten filament, a processing step which could one day become a standard in the light bulb industry.
Traditionally, incandescent light bulbs provide more pleasant light, however they lack the efficiency of fluorescent designs. The new bulb offers the brightness and color of a 100 watt incandescent bulb while using less than 60 watts.
The key is to blast the tungsten filament with an ultra-fast, ultra-powerful laser, which creates beneficial nanostructures on the metal's surface. Describes Professor Guo, "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. 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 pulse lasts a mere femtosecond, and delivers as much power as the entire grid of North America into a needle point size spot. Serendipitously, this strange treatment yields nanostructures and microstructures which turn a low-wattage incandescent light bulb into a high brightness one, while preserving its energy sipping character.
The incredible discovery was made after Professor Guo tinkered with the reverse phenomena -- a laser processed metal that was incredibly good at capturing light, making it almost a perfect black. He figured that if this was possible, the reverse -- a material giving off light much more efficiently -- was also probable. Professor Guo describes, "There is a very interesting 'take more, give more' law in nature governing the amount of light going in and coming out of a material. We knew it should work in theory, but we were still surprised when we turned up the power on this bulb and saw just how much brighter the processed spot was."
The process can also tune the color of the bulb. By controlling the pulse, the resulting nanostructures are modified in a predictable way, in turn modifying the wavelength of the emitted light. Professor Guo has demonstrated blue, golden, and gray designs, in addition to black, white, and the base yellow. The team has even made filaments able to emit polarized light without efficiency-reducing filters.
Funded by the U.S. Air Force Office of Scientific Research, Professor Guo continues to explore what kind of additional changes he can invoke with the laser. And given that the laser he's using can run off a wall socket, there's hope that the discoveries he takes can be ported to production. While materials changes are frequently expensive, this breakthrough would only need capital investments for the laser, which is reusable. Thus it could deliver these super-bulbs at a reasonable price.
The new research is detailed in a paper, appearing in the journal Physical Review Letters.