Making something invisible is common in science fiction, such as the invisibility cloak in Harry Potter. Sure, it sounds cool, but the reason it's so common in stories is that it would be incredibly useful technology. Its use in espionage and military affairs is obvious, but there are more applications.
Given its great utility, it may not be surprising that scientists and engineers have been actively studying it. They have also made considerable progress, using molybdenum trioxide, metamaterials, ultrathin films and dielectric materials to make invisibility cloaks. It all boils down to manipulating light in the right way. It is particularly amazing that innovations in this field can also greatly enhance sensors, telecommunications, encryption and many other technologies.
Space, the last frontier The USS Enterprise continued its mission to explore the Milky Way galaxy when all communication channels were suddenly cut off by an impenetrable nebula. In many plots of the iconic TV series Star Trek, the heroic crew members have to "solve technology with technology" and "solve science with science" in just 45 minutes. Although it took quite a long time in their laboratory, a team of scientists from Rostock university successfully developed a new design method for man-made materials, which can transmit optical signals through precisely adjusted energy flow without any distortion.
"When light travels in an inhomogeneous medium, it experiences scattering." Professor Alexander szameit of the Institute of physics of Rostock University described the starting point of his team's consideration: "This effect quickly converts a compact directional beam into diffuse light. All of us are familiar with summer clouds and autumn fog. It is worth noting that it is the microscopic density distribution of a material that determines the specific details of scattering. The basic idea of induced transparency is to use a little-known optical property to clear the way for the beam, so to speak."
This second characteristic, known in the field of photonics as the mysterious title of non constancy, describes the flow of energy, or more accurately, the amplification and attenuation of light beams. Intuitively, the related effects seem undesirable -- especially the beam attenuation due to absorption, which seems to have a great reaction to the task of improving signal transmission. However, non Hermite effect has become a key aspect of modern optics. The whole research field is trying to use the complex interaction of loss and amplification to achieve advanced functions.
The first author of this paper Andrea steinfurth, a doctoral student, said: "This method opens up new possibilities. With regard to a beam of light, it is possible to selectively amplify or suppress specific parts of the beam at the micro level to offset any degradation. In order to remain in the picture of the nebula, its light scattering characteristics can be completely suppressed. We are actively modifying a material to transmit specific light signals as much as possible. For this reason, the energy flow must be accurately controlled, so it can It is combined with materials and signals like pieces of a jigsaw puzzle. "
Researchers at Rostock University have successfully met this challenge by working closely with partners at the Vienna Institute of technology. In their experiments, they were able to reproduce and observe the microscopic interaction between optical signals and their newly developed active materials in a kilometer long optical fiber network.
In fact, induced transparency is just one of the fascinating possibilities of these findings. If you really want to make an object disappear, just preventing scattering is not enough. Instead, light waves must appear completely undisturbed behind them. However, even in the vacuum of space, diffraction alone can ensure that any signal will inevitably change its shape. "Our research provides a formula for constructing materials in such a way that when the light beam passes through, it seems as if the material and the space area it occupies do not exist. Even the Romulus' fictional stealth device cannot do this," said co-author Dr. Matthias Heinrich, which goes back to the last frontier of star Trek.
The findings in this work represent a breakthrough in the basic research of non Hermite photonics, and provide a new method for active fine-tuning of sensitive optical systems, such as medical sensors. Other potential applications include optical encryption and secure data transmission, as well as the synthesis of multifunctional artificial materials with customized properties.