Scientists at the University of Rostock have devised a revolutionary technology that may make artificial materials transparent or even completely invisible on demand, in partnership with researchers from the Vienna University of Technology. Their discovery was recently published in Science Advances, a prestigious magazine.
In science fiction, such as Harry Potter’s Cloak of Invisibility, making anything invisible is a recurring trope. It certainly sounds nice, but the reason it appears so frequently in stories is because it would be an extremely valuable piece of technology. There are obvious applications for espionage and the military, but there are many more.
Given its great utility, it should come as no surprise that scientists and engineers have been working on this for some time. They’ve made significant progress as well, constructing invisibility cloaks out of molybdenum trioxide, metamaterials, metascreens, and dielectric materials. It all boils down to properly manipulating light, and what’s even more amazing is that advancements in this field can improve sensors, telecommunications, encryption, and a variety of other technologies.
Many episodes of the renowned television series Star Trek need the brave crew to ‘tech the tech’ and ‘science the science’ within 45 minutes of broadcast in order to aid their escape from this or a similar situation before the end credits roll. A team of scientists from the University of Rostock succeeded in inventing an entirely new approach for the design of artificial materials that can transfer light signals without distortions using precisely calibrated energy flows despite spending much more time in their laboratory.
“Light scatters when it spreads across an inhomogeneous material.” Professor Alexander Szameit of the Institute for Physics at the University of Rostock summarizes the beginning point of his team’s considerations: “This effect swiftly turns a compact, directed beam into a diffuse glow, and is familiar to all of us from summer clouds and fall fog alike.” The characteristics of scattering are determined by the tiny density distribution of a substance. “The basic notion of induced transparency is to take advantage of a much lesser-known optical feature to create a way for the beam, in a sense,” Szameit explains.
The movement of energy, or, more correctly, the amplification and attenuation of light, is described by the second attribute, known in the field of photonics as non-Hermiticity. Intuitively, the accompanying consequences may appear to be undesired — fading of a light beam owing to absorption, for example, would appear to be highly detrimental to the objective of increasing signal transmission. Non-Hermitian effects, on the other hand, have become an important part of modern optics, and an entire field of research is dedicated to harnessing the complex interplay of losses and amplification for new functionality.