Researchers at the University of Rochester discovered a way to trap light for a period of nanoseconds, longer than light has ever been confined to a small space. Using a nanostructure of silicon, the scientists produced an algorithm based on genetic principles to create a nanocavity (silicon wafer) 10 times more effective than other nanocavities in confining light.

The nanocavity traps light in a region approximately one hundredth the width of a human hair (one-half millionth of a meter). The amount of time for which researchers trapped the light in this study is normally the amount of time it would take light to travel many meters.

"Light holds the key to some of nature's deepest secrets, but it is very challenging to confine it in small spaces," says Antonio Badolato, the corresponding author of the study published in Applied Physics Letters. "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."

Badolato's team, including Ph.D. student Yiming Lai and researchers from Ecole Polytechnique Federale in Switzerland and Universita di Pavia in Italy, perfected an algorithm that allowed them to create a combination of the most functional nanocavities to trap light. They treated each nanocavity as an individual, and combined "individuals" to create new nanocavities. The algorithm processed the functional quality of the nanocavities and selected the ones that trapped light for the longest time, creating more nanocavities from those.

Using such theories from genetics and evolutionary biology allowed the research team to create these complex and incredibly effective nanophotonic structures. The structures, while opening up many possibilities, also maintain a relatively small footprint, making Badolato's feat even more innovative.

The behavior of light as a particle is a fundamental level of study in nanophysics, and this discovery is a step towards further understanding it. Confining light allows for more effective and easier control and coupling to devices such as nanophotonic circuits. These circuits will soon improve technologies such as telecommunications and biosensing by processing light incredibly fast, without consuming high amounts of energy.

The medical applications for these nanophotonic structures are compelling. Biosensing devices using Badolato's nanocavities could analyze single drops of blood for biomaterials such as viruses that may attach near trapped light. The research team is currently working with University of Rochester's Medical Center to find out more.

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