Light has no mass when it is at rest, but that never happens - photons are always traveling. They can be slowed down (this is how a curved glass lens bends light), but they can never be stopped.
Researchers at the University of Rochester developed a way of trapping photons of light in a very small space for a (relatively) long period of time. This was accomplished using a nanocavity.
These are ultrafine channels cut into a silicon wafer, and hold light in a space roughly one-hundred the width of a human hair.
Light was confined to these channels for a few billionths of a second. This is roughly 10 times longer than had ever before been achieved. During this time, light would normally travel hundreds of feet.
"Light holds the key to some of nature's deepest secrets, but it is very challenging to confine it in small spaces. Light has no rest mass or charge that allow forces to act on it and trap it; it has to be done by carefully designing tiny mirrors that reflect light millions of times," Antonio Badolato of the University of Rochester, said.
Lasers also work, in part, by bouncing light between a pair of mirrors.
Researchers are interested in trapping light, in part, because it allows study of electromagnetic forces under conditions where they act more like particles than waves. This state of light examined in a study won the Nobel Prize in physics in 2012.
Nanocavities are traditionally designed using the best knowledge of researchers, but without an algorithm to design the channel.
Badolato, with graduate student Yiming Lai, created a mathematical model for the channels. The model uses an evolutionary algorithm tool to determine the most - and least - important factors in nanocavity creation. Computer simulations treated a variety of designs as breeding individuals. When two designs came together, a new design would be produced, with aspects of each "parent." Those with the longest holding times left the greatest number of "offspring," creating constantly-improving designs.
Integrated nanophotonics could, one day, lead to revolutionary advances in information-handling, telecommunications and biosensing, devices that combine biological and chemical sensors.
These systems would operate using very little electricity, and would be highly sensitive to changes in their immediate environments. This property allows the system to recognize a virus near the channel. This could be used to develop a new generation of medical detectors.
Development of the silicon nanocavity and trapping of photons was profiled in the journal Applied Physics Letters.
