![]() ![]() What Mikhail’s done-and it’s admittedly simple to calculate-is to show that if you use a light-absorbing film like germanium, much thinner than the wavelength of light, then you can still see large interference effects.” In this particular case there was almost a bias among engineers that if you’re using interference, the waves have to bounce many times, so the material had better be transparent. ![]() “If you have perceptive eyes, as many of my students do, you can discover exciting things that have been overlooked. “In my group, we frequently reexamine old phenomena, where you think everything’s already known,” Capasso says. Kats carried that theme into the realm of color. Graduate student and lead author Mikhail A. The common thread in Capasso’s recent work is the manipulation of light at the interface of materials that are engineered at the nano- scale, a field referred to as nanophotonics. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS, whose research group most recently produced ultrathin flat lenses and needle light beams that skim the surface of metals. The discovery is the latest to emerge from the laboratory of Federico Capasso, Robert L. Published in the journal Nature Materials (online) on October 14, the finding opens up new possibilities for sophisticated optical devices, as well as consumer products such as jewelry and new techniques in the visual arts. Harvard physicists have now discovered that even very “lossy" thin films, if atomically thin, can be tailored to reflect a particular range of dramatic and vivid colors. The colors form the logo of the Harvard School of Engineering and Applied Sciences (SEAS), where researchers have demonstrated a new way to customize the color of metal surfaces by exploiting a completely overlooked optical phenomenon.įor centuries it was thought that thin-film interference effects, such as those that cause oily pavements to reflect a rainbow of swirling colors, could not occur in opaque materials. ![]() A centimeter to the right, where the same metallic coating is literally only about 20 atoms thicker, the surface is a dark blue, almost black. – Octo– In Harvard’s Pierce Hall, the surface of a small germanium-coated gold sheet shines vividly in crimson. (Photo by Eliza Grinnell, SEAS Communications.)Ĭambridge, Mass. Romain Blanchard, Mikhail Kats, and Patrice Genevet, members of Federico Capasso's research group at Harvard SEAS. (Photo courtesy of Mikhail Kats, Romain Blanchard, and Patrice Genevet.) Gold films colored with nanometer-thick layers of germanium. ![]()
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