Lasers and… modern alchemy?

Now this is a cool discovery. Turns out the old idea of making gold from other metals is not as far fetched as you might think! Well, okay, so we can’t really turn metal into gold – but we can make it look like gold! At least, one scientist at the University of Rochester has figured out a way to do just that with lasers.

Dr. Chunlei Guo, professor of optics, published the paper in the journal Applied Physics Letters in January entitled “Colorizing metals with femtosecond laser pulses.” In it, the authors describe their technique of using extremely short laser burst to alter the surface of a metal. These bursts – lasting only quadrillionths of a second - melt and vaporize the atoms on the surface, which subsequently rearrange themselves in nanostructures. These nanostructures include holes, globes and rods. These structures respond to incoming light in new ways from the original atomic structure; their reflection of light is highly dependent on their size and shape. So simply by changing the laser, Dr. Guo can change the resulting nanostructures, and thus change the reflected light to be a different color. This process is different from a coating or a finish, since it actually physically changes the properties of the metal. So it won’t wear away, peel or fade. And it cannot be felt by your finger. The altered structures are simply too small for our nerves to detect, so the metal still feels like normal. As far as we are able to detect, a golden aluminum that results from this method is indistinguishable from real gold.

So far, Dr. Guo has been able to make aluminum, platinum, titanium and silver look like pure gold. For that matter, he’s also made them look black, blue and gray. And he believes he can create any color he wishes, including multi-colored iridescence like the wings of a butterfly. It’s only a matter or trial and error to find the right setting for the lasers and the metal.

So what’s the practical use of this technique? Dr. Guo has suggested uses from the fanciful – etching a family photo on the metal door of a refrigerator – to the practical – producing cars and bicycles of different colors without having to use paint. Or, perhaps, custom-designing jewelry to match the eyes of your beloved? Apparently he’s already been contacted by jewelers about that possibility.