Design Of Eectromagnetic Invisibility Cloak By The Optical Transformation Theory

With the booming of the artificial electromagnetic meta-materials, people are committed to designing a variety of electromagnetic invisibility devices. Optical transformation principle aims to provide a valid theoretical guidance. The most traditional electromagnetic invisibility device is called an internal device that can guide electromagnetic waves to bypass the target object to be cloaked, as if the electromagnetic wave propagation in free space. However, the traditional internal invisibility device is located outside the target object to be hidden, which led to no communication between the target object and the outside. In order to achieve the communication between the target object and the outside world, researchers have proposed various electromagnetic cloak designs. One of greatest improvements among them is the external electromagnetic invisibility device according to the principles of complementary media. The target object to be cloaked is located outside the complementary media invisibility cloak, and we also introduce an appropriate image objects according to a specific target object. Such external electromagnetic invisibility cloak depending on complementary media principles can communicate with the outside well. Simultaneously, the complementary media electromagnetic invisibility cloak also has the effect to get an illusion goals. Based on the principle of optical transformation,we proposed several electromagnetic invisibility devices. The main research work and innovations are as follows:1. A minimized invisibility complementary cloak with a composite shape have been designed. Based on the transformation optics and the concept of complementary media,we develops a minimized external invisibility cloak. The proposed cloak composed of a circular sector and two triangle sectors makes this invisible device with a smaller size compared with the complementary cylinder cloak. With the complementary media, the target object to be hidden can be placed at the outside of the cloak, and thus the target object can receive the external electromagnetic waves. Full-wave simulation results demonstrate that the proposed complementary invisibility cloak has a good performance for cloaking multiple target objects and simultaneously generating the illusion images.2. A complementary illusion cloak to hide objects with arbitrary shapes and sizes havebeen developed. In the proposed cloak, a complementary cloak is first introduced by using trapezoid coordinate transformation. Then an illusion device in terms of another trapezoid coordinate transformation is generated to cloak the object. With two coordinate transformations, the required anti-object used to cloak the object is obviously compressed, and the complementary illusion cloak we proposed could hide the target object at any position. Numerical results including target objects of different shapes are given to verify the correctness and effectiveness of the proposed cloak.3. The three-dimensional internal invisibility cloaks and the three-dimensional external invisibility cloaks with arbitrary shape have been studied. With the conformal boundaries in the spherical coordinate system, the design of the 3D electromagnetic invisibility devices with arbitrary shapes was proposed. According to the boundary functions of the invisibility device, we can deduce the formula for calculating the material parameters required by the cloak. General material parameters formulas are directly given, which greatly simplify the design process.