Rochester, NY -- University of Rochester optical scientists have recently discovered that, by using a tabletop laser, they can change the color of a metal.  The innovation began when Chunlei Guo used laser light to change the properties in various metals to turn them black.  Because it was the metals themselves that were altered, there was no risk of the color peeling off.  Now, one year later, the associate professor believes that it is possible to turn any metal any color—or even a variety of colors.

The applications for this process, which is detailed in today’s “Applied Physics Letters”, run deep for the jewelry industry, although that was not at all Guo’s motivation.  “Since the discovery of the black metal, we’ve been determined to get full control on getting metals to reflect only a certain color and absorb the rest,” he explains.  “And now we can finally make a metal reflect almost any color we wish”.  With the help of assistant Anatoliy Vorobeyv, Guo found that using a very brief but intense laser burst changes the surface of a metal, creating nanoscale and microscale structures that reflect only a certain color, giving the appearance of that color.  They have also been successful in creating multi-color combinations. 

With this technology, it is possible to have black platinum, gold silver, blue titanium, purple gold, and any other combination.  It works on every metal tested.  For the jewelry industry, this could mean that the choices for the enormous markets for engagement rings, wedding rings, and other jewelry could be almost infinitely multiplied.  Guo’s discovery can forever change the face of a previously-static market.

The light that Guo uses to change the properties—and, therefore, colors—of metals is a femtosecond laser, producing pulses lasting quadrillionths of a second.  During that period of time, which is likened to the relationship between a full second and 32 million years, the laser releases as much power as all of the electricity in North America, and focuses it onto a needlepoint-sized spot.  By varying the intensity of the laser, the number of pulses, and the length of the pulses, Guo is able to control how the nanostructures in the metal are rearranged, changing what color the metal reflects. 

Right now, it takes more than half an hour to change the color of a spot the size of a dime, but Guo and Vorobeyv are constantly improving the process.  Once the technique is fully refined, the laser can be powered by any normal wall socket.  And the government awaits the perfection of this.  The applications for altering the color of metals have a number of ecological, technological, and economic benefits ranging from advanced stealth technology to more efficient solar energy collection to etching a full-color photograph into the hood of a car.

And, for jewelry lovers, it can mean choosing not only from yellow and white gold, platinum, and the occasional rose gold, but from any color and on any metal.  It will revolutionize the industry, some day.   

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