Studies of invisibility cloak based on structured dielectric artificial materials

The invisibility cloak is the device that prevents the system including the cloak and the concealed target from detection. In 2006, the first invisibility cloak was realized for operating at microwave frequencies. That cloak was made of the resonant metamaterials composed of metallic inclusions. Such success inspired the intensive study on the invisibility devices for the last decade. However, the existing invisibility systems have the limitations in common that deteriorate the cloak efficiency and challenge the implementation. In this dissertation, we proposed the approaches to design the invisibility cloaks composed of the dielectric artificial materials in order to improve the cloaking performance and bring the cloaks to the practical. To reduce the complexity of implementation and broaden the operating bandwidth, the transmission cloak composed of the arrays of identical high permittivity dielectric cylinders was designed. The spatially dispersive profile of the effective refractive index was manipulated by controlling the periodicities of the array sections. The designed cloak achieved to guide the electromagnetic wave bypassing the concealed region at broadband in the full-wave simulations. To further enhance the bandwidth, reduce the complexity and accommodate large targets, we proposed the geometrical optics based transmission cloaks composed of the optical elements, i.e. prisms/lenses, made of homogenous and isotropic dielectric materials. The 2D cloak operating for TM incidence efficiently hide large targets at multiple bands with broad bandwidths in the simulations since the cloak possesses the preservation of both the energy and the phase. Based on the 2D cloak, two types of 3D cloaks, i.e. the extrusion cloaks and the rotation cloaks, were developed. The cloaking capability of the former type was confirmed computationally and experimentally. The latter type also achieved cloaking effect in the simulations, which showed the advantage of low sensitivity to the incident waves’ polarizations and the great promise to the implementation. Furthermore, the superluminal effect supported in the photonic crystals made of high permittivity dielectrics was applied to the transmission cloak that was designed based on transformation optics. Following such approach, the elements in the cloak medium could exceed the subwavelength and operate off resonance