In this paper, we report the fabrication of a homogeneous anisotropic invisibility carpet cloak that works for transverse magnetic (TM) wave in free space. Linear coordinate transformation is employed for the design of the dielectric tensors, and the cloak is made of Al2O3 slabs with a Teflon background. The triangular invisible region has a height of 32.4 mm (one third of the height of the whole device) and a width of 200 mm. The cloaking effect is examined in far-field free-space transmission experiments by measuring the scattering parameters. The results show our device has very good cloaking performance in a wide frequency range from 8 to 12 GHz.

In this paper, we report a fabrication of a three-dimensional (3D) carpet cloak that works for any polarization in free space. Two-dimensional (2D) conformal mapping is first employed and the 3D structure is generated by a rotation of the 2D cloak. The structure of the cloak is hole-in-dielectric. The triangular invisible region has a height of 36 mm (one third of the height of the whole device) and a width of 240 mm. The cloaking effect is examined in free space by measuring the scattering parameters. The results show our device has very good cloaking performance in a wide frequency range from 4 to 10 GHz.

Luneburg lenses are able to form perfect focus that is free of aberration. Because of the varying refractive index throughout the lens, incoming electromagnetic waves can travel in a curved path and be guided to focus at the back of the lens. The implementation of Luneburg lenses is often difficult due to the challenges in creating a medium with varying refractive index using normal materials. This problem can be overcome with the use of gradient index metamaterials. We report a two dimensional Luneburg lens made of gradient index metamaterials. It consists of 17 concentric shells with etched patterns on a printed circuit board working in microwave X band frequency. The broad properties of the Luneburg lens are then discussed.

We present a device that is designed with varying permittivity ε(r) such that an electromagnetic wave in the K-band of the microwave regime entering it will bend inward towards the core. The core is made of silicon composites. We follow the distribution formula of the permittivity for the device derived by Narimanov and Kildishev using the optical-mechanical analogy. The diameter of the device is 14 cm, and it is constructed out of 21 rings of two different types of etched printed circuit boards, as well as dielectric powders as adding filling materials. The experimental wave intensity profile, based on parallel plate measurements for the cases where the incident plane wave is slightly displaced to the top of the center of the device and the case of on center incidence, are presented and discussed. In spite of some mismatch of the core and metamaterial structures of the device found, approximately 80% of the wave still manages to reach the core of the device and gets trapped and absorbed. Broadband properties of the device are also investigated.