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Scientists Turn Objects Invisible Without Metamaterial Coating

Sunday, April 21, 2019

A team of scientists from ITMO University, Ioffe Institute, and Australian National University have discovered a way to render homogenous cylindrical objects completely invisible without metamaterial coating. The method used for the experiment was based on a new understanding of electromagnetic wave scattering. In the study, the scientists examined light scattering from a glass cylinder filled with water whose refractive index could be regulated by changing temperature. They observed that a high refractive index was associated with two types of scattering mechanisms: resonant scattering and non-resonant scattering. According to the study, the resonant scattering was said to be related to the localization of light inside the cylinder. Meanwhile, the non-resonant scattering mechanism is characterized by smooth dependence on the wave frequency. Together, their interaction is known as Fano resonances. When subjected to certain frequencies, the waves scattered via resonant and non-resonant mechanisms develop opposite phases and mutually destroy the other, rendering the object invisible. From their observations, the physicists were then able to successfully apply their new technique and create an invisible homogeneous object. Additionally, by changing the temperature of the water in the cylinder from 90 °C to 50 °C, the team was able to switch the object’s visibility state at a constant frequency of 1.9 GHz through the new scattering cancellation method. "Our theoretical calculations were successfully tested in microwave experiments. What matters is that the invisibility idea we implemented in our work can be applied to other electromagnetic wave ranges, including to the visible range. Materials with corresponding refractive index are either long known or can be developed at will," said Mikhail Rybin, first author of the paper and senior researcher at the Metamaterials Laboratory in ITMO University. Currently, the more popular method for rendering objects invisible requires the use of metamaterial coatings. Metamaterials are artificially designed structures with optical properties not found in nature. These structures possess the ability to change the direction of light, including making it curve around a cloaked object. Recent experiments have also developed methods allowing microwaves to bend around objects, allowing a person to see through the object. However, metamaterials have been known to be difficult to fabricate and incompatible with several invisibility ideas. The newly discovered method presents a more cost-effective and easier to produce alternative to metamaterial coatings. It also gives way to possible developments in nanoantennas, where invisible structural elements could aid in reducing disturbances. As an example, a miniature antenna complex connecting two optical chips could use invisible rods as supports. High-quality instruments and supplies play an essential role in scientific research to produce precise and accurate results. Andwin Scientific supplies over a million laboratory equipment and supplies from an extensive group of leading manufacturers. View our full product line by visiting http://andwinsci.com/categories.php today.