Triple-wave cloaking for electromagnetic and acoustic biphysical invisibilities

There have been attempts to cloak an object from 𝐻𝑧 - polarized electromagnetic waves and sound waves, but it has been difficult to achieve satisfactory high performance. Associate Professor Garuda Fujii of Shinshu University with Associate Professor Youhei Akimoto of the University of Tsukuba realized a triple-wave cloaking effect in addition to the 𝐻𝑧 - polarized electromagnetic wave and sound wave making it possible to cloak an object from 𝐸𝑧 - polarized electromagnetic wave. High performance was confirmed with quantitative evaluation. With the study, Electromagnetic-acoustic biphysical cloak designed through topology optimization, published in the journal Optics Express, it is now possible to select materials that make up the cloaking from materials other than metal.

Furthermore, this is possible even with the combination of sound waves and electromagnetic waves of different wavelengths or when the sound waves have a longer wavelength than the electromagnetic waves. This now makes a triple-wave cloaking effect possible with one device, despite it being difficult to be achieved using just transformation theory and metamaterials.

Creating a cloak for three waves has been very challenging. Only now has it been made possible through topology optimization, however, the realization of the triple-wave cloaking is limited to the numerical computation.  Associate Professor Fujii has supplied the STL of the optimized structure composed of ABS in the Supplementary Material section of the paper, so he hopes other researchers try the experiment.

Since the choice of materials has been expanded, it is expected that the function of the biphysical cloak will also be expanded. In the future, Associate Professor Fujii hopes to optimize the topology of a biphysical cloak, which can cloak obstacles from the combination of wave system and diffusion system.

###

For more information on Associate Professor Garuda Fujii's work please visit his website: http://www.kankyo.shinshu-u.ac.jp/~garudalab/html/index_en.html