Lasers turn pure aluminum … ‘gold’

The ultimate goal of the Old World alchemist was to turn inexpensive metals into gold.

Mar 1st, 2008
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The ultimate goal of the Old World alchemist was to turn inexpensive metals into gold. Modern-day physicists at the University of Rochester’s Institute of Optics (Rochester, NY), have turned aluminum and other metals gold—in color if not chemistry. A femtosecond laser processing technique created by professor Chunlei Guo and his assistant Anatoliy Vorobeyv alters the surface properties of aluminum, platinum, titanium, tungsten, silver, and gold to create tints of gold, blue, gray, black, and even multicolored irridescence.

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The technique involved a Ti:sapphire laser system emitting 800 nm, 65 fs pulses at about 1.1 mJ/pulse. The horizontally polarized laser beam can modify single spots as small as 10 µm in size, or large areas using a scanned laser beam. The laser induces periodic nanostructures that change the reflectance and absorption properties of incoming light. As the simple technique is refined, says Guo, possible applications could include using a single laser to create colored metal bike frames, etching full-color pictures of your family onto your refrigerator door, or creating an engagement ring the color of your fiancé’s eyes. Contact Chunlei Guo at guo@optics.rochester.edu.

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