By harnessing the power of tiny waves dancing in an electron sea, Japanese physicists have developed a novel way to project holograms that don’t change color when you move your head.
“In a conventional hologram, if you change the angle, the color changes,” said optical physicist Satoshi Kawata of Osaka University in Japan. “Our hologram shows natural color at any angle you observe.”
The researchers’ machine takes advantage of how beams of light trigger waves of activity in free electrons, unattached to any atom, arrayed on a metal surface.
Called surface plasmons, these waves could be used to blast cancer cells and build ultra-fast computer processors. They also show up in medieval stained glass windows, where plasmons on flecks of gold suspended in the glass make the window change color as the sun sets.
Plasmons always emit colored light, Kawata says, but it’s usually only visible within a few nanometers of the metal’s surface. But if the light bounces off a ridged surface, it can project far enough from the metal to be seen by the naked eye. In a paper published April 8 in Science, Kawata and colleagues describe how they used surface plasmons to reconstruct a faithful, full-color holograph.