A rainbow trap

Some scientists say they have slowed down then stopped for a splash of light in what is described as a crucial step towards the ultra-fast future of computing.
The technique, called 'trapped rainbow', would help to optical data storage, with light electrons to store information that replaces
controlling light also help engineers control major nodes where billions of optical data packets arrive at the same time.
Slowing some packets to let others through, a bit 'as a system of traffic congestion, the flow of data can be enhanced.
The research, by Professor Ortwin Hess of the University of Surrey, UK and Mr Kosmas Tsakmakidis is based on so-called 'negative refractive index' of metamaterials.
Metamaterials are new materials with metal components that are smaller than the wavelength of light, while the refractive index measures the slowing of light as it passes through an object.
The innovation exploits a principle called the Goos-Hänchen effect, an optical phenomenon discovered 60 years ago that happens to polarized light travels in straight lines.
When this light hits an object or an interface between two media, just do not bounce, but travel along the object.
In the case of metamaterials, light travels backwards along the object.
Hess suggested the creation of a prism sandwich, a tapered layer of glass surrounded by two layers of negative refractive index metamaterials.
A packet of white light injected into the glass from the end of the wide prism slows as it travels down the cone and is then ground to a halt.
The description of how a 'trapped rainbow' derives from the fact that the frequency component of white light are the colors of the rainbow red orange yellow, green, blue, indigo and violet.
Each individual frequency is stopped at a different point down the taper, until the light is stopped.
'It is like wading through snow, but becomes slower and slower, " said Hess.
The researchers say that by exploiting the different frequencies that make up the spectrum of light and slow, stop and capture these frequencies, the way is open for a boost in mass data management.
"The technique could allow the use of light rather than electrons to store in devices such as computers, allowing an increase in operating capacity by 1000%"
"Previous attempts to slow and capture light have involved extremely low or very low temperatures, have been extremely costly and have only worked with a specific frequency of light at a time."