What makes the new materials different from previous metamaterials is that rather than changing two aspects of the way light moves, they change only one. If light is thought of as a wave, the wave front is perpendicular to the direction the light is moving. Imagine an ocean wave crashing ashore: it’s moving in just one direction, but the wave front is a huge wall of water. Previous metamaterials changed the direction of light beams passing through them, and the wave front remained perpendicular to the direction of the beam. In the new materials, the light beam changes direction, but the wave fronts don’t, giving the impression that they are slipping to the side rather than moving forward. (See image below.)
When a light beam moves through an ordinary material, it moves in the same direction the light waves are facing (top part of image). When a light beam enters a new type of “metamaterial,” it changes direction, but the waves remain facing the same way, seeming to slip sideways (see bottom half of image). This image is from a computer simulation.
Credit: Anthony Hoffman, Princeton University
The overall effect on the direction of the light beam is the same as in the earlier metamaterial, but the new materials are simpler to create, and they absorb far less light, making them more attractive for use in optics.
The first application the Princeton researchers are developing is a flat lens for chemical-sensing devices, an application for which materials that work with infrared light are particularly well suited. Gmachl says that the current optical setups for such devices are bulky because they use conventional lenses. “The first application would be using that material to miniaturize optical setups” by replacing curved lenses with flat ones, she says.
Another early application could be in night-vision devices, which also work with infrared wavelengths. “For people who want to improve night-vision devices, this could be quite interesting,” Smolyaninov says.