The researchers run into a brick wall, however, when it comes to compressing light farther than its wavelength. Light doesn't want to stay inside a space that small, Oulton said.
They have squished light beyond these limits using surface plasmonics, where light binds to electrons allowing it to propagate along the surface of metal. But the waves can only travel short distances along the metal before petering out.
Oulton had been working on combining plasmonics and semiconductors, where these losses are even more pronounced, when he came up with an idea to achieve simultaneously strong confinement of the light and mitigate the losses. His theoretical "hybrid" optical fiber consists of a very thin semiconductor wire placed close to a smooth sheet of silver.
"It's really a very simple geometry, and I was surprised that no one had come up with it before," Oulton said.
Oulton ran computer simulations to test this idea. He found that not only could the light compress into spaces only tens of nanometers wide, but it could travel distances nearly 100 times greater in the simulation than by conventional surface plasmonics alone. Instead of the light moving down the center of the thin wire, as the wire approaches the metal sheet, light waves are trapped in the gap between them, the researchers found.
The research team's technique works because the hybrid system acts like a capacitor, Oulton said, storing energy between the wire and the metal sheet. As the light travels along the gap, it stimulates the build-up of charges on both the wire and the metal, and these charges allow the energy to be sustained for longer distances. This finding flies in the face of the previous dogma that light compression comes with the drawback of short propagation distances, Zhang said.
"Previously, if you wanted to transmit light at a smaller s
|Contact: Rachel Tompa|
University of California - Berkeley