When optical scientists talk of turning light upside down, they aren’t merely thinking of hanging a light bulb in a garage. A more accurate description of this technique would be: the intentional subversion of the hyperbolic metasurface from which light pushes outward. Of course, that’s not really clear either. Optical science and calibration standards are very often an extremely technical subset of the scientific community; so just what were scientists from San Sebastian, Spain reporting in a recent edition of Science?
Let’s start with this: optical waves of light proceed away from their source in a way that is convex (or circular, for an easier concept). They do this in almost every situation, and to date, there has been no known way of switching this convex form on the metasurface. But it had been thought that if the surface the light was moving from was calibrated correctly, a change in this circular format could be possible.
Researchers in Spain may have done just that. Using boron nitride and infrared light, the teams proved that they could indeed stimulate concave light waves. The metasurface is extremely fickle and needs replication on the nano-scale in order to create. The team used a combination of electron beam lithography and the aforementioned boron nitride (in flake form) to achieve the desired results. However, according to researcher Saül Vélez, “the same fabrication methods can also be applied to other materials, which could pave the way to realize artificial metasurface structures with custom-made optical properties.”
So why does the concave or convex shape of wave light even matter beyond the interest of some dedicated scientists? In a very simple sense, much of our modern technology is propelled by optics, and any innovation on that front can lead to a myriad of useful inventions. LEDs are a great example of this; the ways in which they have become integrated in the world is far beyond what was originally envisioned.
In the near future, upside down light (if you will) shows the promise of uncommon metasurface that may open our eyes to new optical techniques. Calibration standards at only the most intense levels will be required to make further progress, but researchers have taken an important first step in unlocking a new code on the light spectrum.