These electron microscope images show an experiment in which Princeton electrical engineer Stephen Chou showed that blocking a hole in a thin metal film could cause more light to pass through the hole than leaving the hole unblocked. The top image shows an array of holes with gold caps, each of which is 40 percent bigger than the hole on which it sits. The bottom image shows a cross-section view of one hole with the cap sitting on top. The hole covered with the cap surprisingly allows more light to be transmitted through the film than a hole without the cap, Chou’s research team found. (Image courtesy of Stephen Chou)
by Steven Schultz Conventional wisdom would say that blocking a hole would prevent light from going through it, but Princeton University engineers have discovered the opposite to be true. A research team has found that placing a metal cap over a small hole in a metal film does not stop the light at all, but rather enhances its transmission. In an example of the extraordinary twists of physics that can occur at very small scales, electrical engineer Stephen Chou and colleagues made an array of tiny holes in a thin metal film, then blocked each hole with an opaque metal cap. When they shined light into the holes, they found that as much as 70 percent more light came through when the holes were blocked than when they were open. "The common wisdom in optics is that if you have a metal film with very small holes and you plug the holes with metal, the light transmission is blocked completely," said Chou, the Joseph Elgin Professor of Engineering. "We were very surprised." Chou said the result could have significant implications and uses. For one, he said, it might require scientists and engineers to rethink techniques they have been using when they want to block all light transmission.
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