Research to make an object invisible (cloaking)

The method of making an object invisible by covering it with a special medium such as films is called cloaking.

There are several methods to make an object invisible. One of them is cloaking. Two well-studied cloaking methods are shown in Fig. 1. (a) in which light is designed to bypass the cloaking medium, requiring a complex metamaterial for the cloaking medium, and (b) a method in which the polarization in the cloaking object is canceled by the cloaking medium.

The design of cloaking media has been dominated by the analytical method of the transformation optics. However, our laboratory has been developing a new method that uses machine learning, such as neural networks and genetic algorithms. Our group uses machine learning and genetic algorithms, such as neural networks, to design cloaking media with higher performance than reported.

In method (b), the cloaking medium can be designed to minimize scattering by obtaining an exact solution using the Mie scattering theory. The fact that the structure obtained in the design achieves cloaking can be confirmed by a numerical electromagnetic simulation called the FDTD method (Fig. 2). Furthermore, our laboratory has shown that cloaking can also be achieved experimentally.