By changing the way light behaves within a meta-surface, a very small synthetic material, these Chinese scientists were able to slow down the speed of light by 10,000 times. This could be useful for computing and optical communication.
Light travels at the speed of light. This is constant: 299,792 km per second. It is an unshakable law of physics, which defines much of the structure of our universe. This constant certainly applies to a vacuum: in water, light naturally slows down. Controlling the slowing down of light, however, is a completely different story.
However, this is what Chinese scientists managed to do by developing a new method, reported in a study published in early 2024 in the journal Nano Letters, spotted by ScienceAlert on February 11. And it’s not just theoretical physics: “ We believe our work opens an entirely new avenue for achieving ultrasolid light-matter interactions in nanophotonic chips. », they write. Clearly, mobilizing this advance on chips could have an impact on computing and optical communication. But how ?
The answer is to be found in the generation of a specific state of matter: electromagnetically induced transparency. This method, already known, consists of electronically disrupting the path of light. Thanks to the use of two optical beams – lasers – the gas in the target medium becomes “transparent” instead of being opaque. Contrary to what one might imagine, this transparent window slows down the light due to a dispersion phenomenon.
A chip specially designed to slow down light
Electromagnetically induced transparency, however, poses a problem. As the light disperses during this slowdown, a large part of it and also its energy are lost. This makes this technique impractical for mobilizing it in real conditions. It is this puzzle that these Chinese scientists wanted to solve.
To do this, they created a specific meta-surface, capable of reducing this loss. By “meta-surface”, we mean a type of 2D material, ultrathin and purely synthetic (not found in nature). In this case, the new meta-surface presented in this study is made up of very thin layers of silicon, in the same way as a computer chip. We are talking about a nanophotonic chip here because it is optical. They designed a completely new structure, where the meta-atoms of the meta-surface are positioned in close proximity to each other.
Their chip makes it possible to reduce energy losses by five times, compared to previous techniques using electromagnetically induced transparency. As for light, its speed is reduced by 10,000 times. Their method works. This is not the first time that light has been slowed down in a controlled environment, but this one is particularly efficient: enough to promise new techniques for the future of computing, which will perhaps also involve quantum computing.
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