A team of Russian and American scientists have discovered a new way to absorb electromagnetic (EM) radiation. Their new technique could be used to improve a broad range of technology, such as photovoltaics, stealth aircraft, sensing, nanochemistry, and a photodynamic therapy (a medical treatment that uses light to kill cancer cells).
Traditionally, EM radiation is absorbed using metamaterials and a technique called destructive interference, which is required in order to avoid back reflections. Now, a group of researchers from Moscow Institute of Physics and Technology, Kansas State University, and the U.S. Naval Research Laboratory have proven otherwise. They demonstrated that destructive interference isn’t necessary for achieving perfect absorption. Instead, they used a natural crystal that has a unique structure that helps to absorb EM waves. Therefore, there is no need for the anti-reflective layer or substrate that is used in the standard destructive interference technique. The crystal, called hexagonal boron nitride, has also been used in optics and nanoelectronics because of its rare properties.
“The ability to fully absorb electromagnetic radiation is one of the key areas of focus in electrodynamics. It is believed that destructive interference is needed to do this, which therefore requires the use of anti-reflective coatings, substrates and other structures. Our observations indicate that interference is not a compulsory requirement and perfect absorption can be achieved using simpler systems,” says researcher Denis Baranov.
There are some limitations that will need to be worked out before the new technique can be practical. The researchers were only able to achieve perfect absorption under limited conditions, with a fixed wavelength an angle of incidence. Still, the research is very important, because it proves that it is possible to completely absorb radiation without destructive interference.
The new technique is described in a paper call “Perfect interferenceless absorption at infrared frequencies by a van der Waals crystal,” which published in Physical Review B.