Scientists have already established that light can be slowed down under certain conditions, and a new study demonstrates a method that promises to be one of the most useful. Researchers from Guangxi University and the Chinese Academy of Sciences in China say their method could benefit the development of computing and optical communications.
In a vacuum, light travels at only one speed - 299,792 kilometers per second. However, if electromagnetic fields appear in its path - such as the fields surrounding matter, this speed will begin to fall.
Most transparent materials slow down light, but not by much. It is the change in its speed that leads to the refraction of light when passing from one medium to another. But to really slow down light, you need special materials, such as photonic crystals or even supercooled quantum gases.
“We believe that our work opens up an entirely new direction for realizing ultra-robust light-matter interactions in nanophotonic chips,” the researchers write in their published paper.
The new method is based on something called electromagnetic-induced transparency (EIT), where special laser techniques are used to manipulate electrons inside a gas stored in a vacuum, turning it from opaque to transparent.
Researchers have taken some of the principles of EIT in light control and developed a new material to slow down light. This material is a kind of metasurface - a synthetic two-dimensional structure with properties unlike anything existing in nature.
The team's metasurfaces were made from very thin layers of silicon, and were much better than existing options for trapping and releasing energy (in this case, light).
According to the results obtained by the researchers, light can be slowed down by more than 10,000 times in this system. At the same time, light losses are reduced by more than five times compared to other similar methods.
Key to the new approach is the way the tiny building blocks of the metasurface, known as meta-atoms, are arranged. In this case, they are close enough to blend into each other, which in turn affects how light is processed as it passes through it.