Connect with us

Hi, what are you looking for?

CleanTechnica

Clean Power

New Way To Filter Light — First Directional Selectivity For Light Waves Achieved By Researchers

An entirely new way to filter light, one that has long been sought but until now remained elusive, has been achieved by researchers at MIT.

For the first time, it’s become possible to selectively filter light according to its direction of propagation — in other words, to filter it based on where it’s coming from.

In this photo of the angular-selective sample (the rectangular region), a beam of white light passes through as if the sample was transparent glass. The red beam, coming in at a different angle, is reflected away, as if the sample was a mirror. The other lines are reflections of the beams. (This setup is immersed in liquid filled with light-scattering ­particles to make the rays visible). Image Credit: Weishun Xu and Yuhao Zhang

In this photo of the angular-selective sample (the rectangular region), a beam of white light passes through as if the sample was transparent glass. The red beam, coming in at a different angle, is reflected away, as if the sample was a mirror. The other lines are reflections of the beams. (This setup is immersed in liquid filled with light-scattering ­particles to make the rays visible). Image Credit: Weishun Xu and Yuhao Zhang

The new system from MIT “allows light of any color to pass through only if it is coming from one specific angle; the technique reflects all light coming from other directions.” This technical breakthrough should lead to advances in solar photovoltaics, telescopes, microscopes, and a number of other consumer products.

“We are excited about this,” states professor of physics Marin Soljačić, “because it is a very fundamental building block in our ability to control light.”


The new system relies on a structure that consists of a stack of ultrathin layers, composed of two alternating materials, where the thickness of each layer is controlled to a precise degree.

“When you have two materials, then generally at the interface between them you will have some reflections,” Soljačić explains. But at these interfaces, “there is this magical angle called the Brewster angle, and when you come in at exactly that angle and the appropriate polarization, there is no reflection at all.”

MIT adds more:

While the amount of light reflected at each of these interfaces is small, by combining many layers with the same properties, most of the light can be reflected away — except for that coming in at precisely the right angle and polarization.

Using a stack of about 80 alternating layers of precise thickness, states MIT graduate student Yichen Shen, “we are able to reflect light at most of the angles, over a very broad band (of colors) the entire visible range of frequencies.”

Previously, the researchers had already demonstrated approaches which allowed for the selective reflecting of light, but these were all very limited with regards to colors. The new approach is considerably different — the breadth will allow for a considerably greater number of applications.

Shen explains: “This could have great applications in energy, and especially in solar thermophotovoltaics — harnessing solar energy by using it to heat a material, which in turn radiates light of a particular color. That light emission can then be harnessed using a photovoltaic cell tuned to make maximum use of that color of light. But for this approach to work, it is essential to limit the heat and light lost to reflections, and re-emission, so the ability to selectively control those reflections could improve efficiency.”

Other potential applications are possible in the fields of microscope and telescope technology. For example, “by using a system that receives light only from a certain angle, such devices could have an improved ability to detect faint targets.”

Another interesting possibility is as a means of improving the privacy of display screens on phones, tablets, computers, etc — with this system applied, products could be made so that only those directly in front of the device would be able to see anything.

The new findings are detailed in a paper published this week in the journal Science.


Appreciate CleanTechnica’s originality? Consider becoming a CleanTechnica Member, Supporter, Technician, or Ambassador — or a patron on Patreon.
 
 
Have a tip for CleanTechnica, want to advertise, or want to suggest a guest for our CleanTech Talk podcast? Contact us here.
Written By

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

Comments

#1 most loved electric vehicle, solar energy, and battery news & analysis site in the world.

 

Support our work today!

Advertisement

Power CleanTechnica: $3/Month

Tesla News Solar News EV News Data Reports

Advertisement

EV Sales Charts, Graphs, & Stats

Advertisement

Our Electric Car Driver Report

30 Electric Car Benefits

Tesla Model 3 Video

Renewable Energy 101 In Depth

solar power facts

Tesla News

EV Reviews

Home Efficiency

You May Also Like

Climate Change

En-ROADS from MIT and Ventana Systems is an interactive climate science tool that lets anyone explore how making changes to the environment can help...

Batteries

A research team at the Massachusetts Institute of Technology (MIT) has taken a deep dive look into lithium-ion battery costs. Grab your wetsuit and...

Cars

For two decades now, the mainstream press has been feeding peoples’ natural skepticism about new technology, dismissing electric vehicles as a quaint fad that...

Clean Power

Commonwealth Fusion Systems says it plans to build a compact, affordable fusion reactor that will begin generating electricity in 10 years.

Copyright © 2021 CleanTechnica. The content produced by this site is for entertainment purposes only. Opinions and comments published on this site may not be sanctioned by and do not necessarily represent the views of CleanTechnica, its owners, sponsors, affiliates, or subsidiaries.