Researchers have now created a new way to control light, depending on the angle at which the light hits it. At a certain angle, light is permitted to pass through, though light coming from any other angle is reflected off, like a mirror. The research was led by Marin Soljačić from the Massachusetts Institute of Technology and the results have been published in Science.
Scientists have long known how to control the transmission of light based on wavelength, direction and polarization however now scientists have found a way to limit what light is transmitted through based solely on the angle from which it comes.
The device works by precisely stacking layers of ultra thin materials alternating between two different types. These layers together will provide a reflective surface there is also a very specific angle, dubbed the Brewster angle, which actually allows light to be transmitted through like a regular pane of glass.
For this experiment, the researchers alternated layers of glass with tantalum oxide, though the team says that any two materials that do not share refractive indices would cause the same effect. Currently, they have created an angle of selectivity of about 10 degrees which allows light through. Though 80 layers were used during this trial, adding more layers would cause the Brewster angle to be much narrower and specific.
So what can we do with this technology? For starters, there are some pretty cool implications in terms of gathering solar energy. When light hits a certain material and heats it up, a certain wavelength of color radiates off it. Solar-harnessing voltaic cells could be used to collect that specific color and convert it into energy. However, this approach requires a great deal of sensitivity in regulating the reflection so that excessive amounts of light and heat aren’t lost.
Additionally, lenses made with this device could be used in telescopes and microscopes to better view objects that might not be very well lit in comparison to other nearby items. In the case of observing a faint star, only the light from the desired star would be permitted to pass through to the observer’s eye; the bright light coming from the moon or brighter stars would be reflected away.
There are also privacy applications in terms of making these panels into computer or smartphone screens. That would allow the user, sitting directly in front of the screen, to view the content, but light would be reflected away for anybody trying to catch a glimpse from a different angle.