Shades of Harry Potter’s invisibility cloak! A recent study in Optica describes a new way to achieve cloaking invisibility. In this method, researchers manipulated the frequency (color) of light waves passing through an object. This approach overcomes critical shortcomings in existing cloaking technologies. The research team says that this technique could help to secure data sent over optical fiber. It could also improve current technologies for sensing, telecommunications and information processing.
Most current cloaking devices can only conceal an object when it is illuminated with just one color of light. However, sunlight and most other light sources are broadband (i.e., they contain many colors). Also, typical cloaking solutions work by changing the dispersion path of the light around the object to be concealed.
The new solution avoids these problems by allowing light waves to pass through the object, rather than around it, while still avoiding any interaction between the light waves and the object.
To achieve this, the researchers rearranged different colors of broadband light so that the light waves passed through the object without actually “seeing” it. For example, if the object reflected green light, they would then change light in the green portion of the spectrum to another color. In this way, there would be no green light for the object to reflect. Then, once the light wave cleared the object, the cloaking device reversed the shift, returning the wave to its original state.
This spectral cloaking device could be useful in working with current telecommunication networks. These systems use broadband waves as data signals to transmit information over optical fiber. Spectral cloaking could selectively determine which operations are applied to a light wave and which are “made invisible” over certain periods of time. Service providers could use this capability to prevent eavesdroppers from gathering information by probing a fiber optic network with broadband light.
Also, providers could transmit more data over a given line by selectively removing and then reinstating colors that are used as telecommunication data signals. This capability could help to reduce “logjams” as data demands continue to explode.